Number Theory Interview Questions

Array Math Dynamic Programming Number Theory Euclidean Algorithm Greatest Common Divisor

Rank

#2301HardFrequency: 73.2%

Count Array Pairs Divisible by K

Asked at PayPal

Array Hash Table Math Counting Number Theory Euclidean Algorithm Greatest Common Divisor

Rank

#2415HardFrequency: 67.6%

Count the Number of Ideal Arrays

Math Dynamic Programming Combinatorics Number Theory Prime Factorization Fermat's Little Theorem

Rank

#4215HardFrequency: 67.6%

Good Subsequence Queries

Array Math Segment Tree Number Theory

Rank

#3989HardFrequency: 62.5%

Sum of Beautiful Subsequences

Array Math Binary Indexed Tree Number Theory

Rank

#3294MediumFrequency: 55.1%

Number of Self-Divisible Permutations

Asked at Salesforce

Array Math Dynamic Programming Backtracking Bit Manipulation Number Theory Bitmask

Rank

#2610MediumFrequency: 54.4%

Closest Prime Numbers in Range

Asked at TikTok

Math Number Theory Primality Test Sieve Theory Prime Number Sieve

Rank

#3244MediumFrequency: 53.4%

Minimize Length of Array Using Operations

Asked at Oracle

Rank

#204MediumFrequency: 47.3%

Count Primes

Array Math Enumeration Number Theory Primality Test Sieve Theory Prime Number Sieve

Rank

#2423HardFrequency: 44.7%

Minimum Deletions to Make Array Divisible

Array Math Sorting Heap (Priority Queue)Number Theory Euclidean Algorithm Greatest Common Divisor

#10

Rank

#4065HardFrequency: 44.7%

Count Sequences to K

Array Math Dynamic Programming Memoization Number Theory

#11

Rank

#1585MediumFrequency: 43.6%

The kth Factor of n

Math Number Theory Prime Factorization

#12

Rank

#258EasyFrequency: 43.3%

Add Digits

Math Simulation Number Theory

#13

Rank

#2324MediumFrequency: 40.8%

Find Triangular Sum of an Array

Array Math Simulation Combinatorics Number Theory

#14

Rank

#3949MediumFrequency: 35.1%

Minimum Number of Primes to Sum to Target

Array Math Dynamic Programming Number Theory

#15

Rank

#2307HardFrequency: 33.5%

Replace Non-Coprime Numbers in Array

Array Math Stack Number Theory Least Common Multiple Greatest Common Divisor

#16

Rank

#3273MediumFrequency: 33.3%

Most Expensive Item That Can Not Be Bought

Math Dynamic Programming Number Theory

#17

Rank

#3655MediumFrequency: 32.8%

Digit Operations to Make Two Integers Equal

Math Graph Theory Heap (Priority Queue)Number Theory Shortest Path

#18

Rank

#1947HardFrequency: 31.3%

Number of Different Subsequences GCDs

Array Math Counting Number Theory Euclidean Algorithm Greatest Common Divisor

#19

Rank

#4242MediumFrequency: 29.1%

Sum of GCD of Formed Pairs

Array Math Two Pointers Sorting Simulation Number Theory

#20

Rank

#1223HardFrequency: 27.8%

Graph Connectivity With Threshold

Array Math Union-Find Number Theory

#21

Rank

#3933MediumFrequency: 27.8%

Minimum Jumps to Reach End via Prime Teleportation

Array Hash Table Math Breadth-First Search Number Theory

#22

Rank

#1936HardFrequency: 27.3%

Maximize Number of Nice Divisors

Math Recursion Number Theory

#23

Rank

#2083EasyFrequency: 27.3%

Three Divisors

Math Enumeration Number Theory Prime Factorization Sieve Theory

#24

Rank

#2125HardFrequency: 26.5%

GCD Sort of an Array

Array Math Union-Find Sorting Number Theory Prime Factorization Euclidean Algorithm Greatest Common Divisor

#25

Rank

#3768EasyFrequency: 26.5%

Check If Digits Are Equal in String After Operations I

Math String Simulation Combinatorics Number Theory

#26

Rank

#950EasyFrequency: 24.4%

X of a Kind in a Deck of Cards

Array Hash Table Math Counting Number Theory Euclidean Algorithm Greatest Common Divisor

#27

Rank

#3210MediumFrequency: 23.6%

Count Beautiful Substrings I

Hash Table Math String Enumeration Number Theory Prefix Sum

#28

Rank

#3920HardFrequency: 23.6%

Minimum Stability Factor of Array

Array Math Binary Search Greedy Segment Tree Number Theory

#29

Rank

#4301MediumFrequency: 23.6%

Minimize Array Sum Using Divisible Replacements

Array Hash Table Math Greedy Number Theory

#30

Rank

#989HardFrequency: 22.1%

Largest Component Size by Common Factor

Array Hash Table Math Union-Find Number Theory Prime Factorization

#31

Rank

#3888HardFrequency: 20.9%

Maximize Subarray GCD Score

Array Math Enumeration Number Theory

#32

Rank

#897MediumFrequency: 20.3%

Prime Palindrome

Math Number Theory Primality Test

#33

Rank

#1836HardFrequency: 20%

Count Ways to Make Array With Product

Array Math Dynamic Programming Combinatorics Number Theory Prime Factorization Fermat's Little Theorem

#34

Rank

#3208HardFrequency: 20%

Count Beautiful Substrings II

Hash Table Math String Number Theory Prefix Sum

#35

Rank

#2716MediumFrequency: 19.5%

Prime Subtraction Operation

Array Math Binary Search Greedy Number Theory

#36

Rank

#1543MediumFrequency: 18%

Simplified Fractions

Math String Number Theory Euclidean Algorithm Greatest Common Divisor

#37

Rank

#1728HardFrequency: 18%

Fancy Sequence

Math Design Segment Tree Number Theory Fermat's Little Theorem

#38

Rank

#2491EasyFrequency: 18%

Smallest Even Multiple

#39

Rank

#1875HardFrequency: 16.4%

Tree of Coprimes

Array Math Tree Depth-First Search Number Theory

#40

Rank

#2367MediumFrequency: 16.4%

Minimum Lines to Represent a Line Chart

Array Math Geometry Sorting Number Theory

#41

Rank

#3314MediumFrequency: 16.4%

Most Frequent Prime

Array Hash Table Math Matrix Counting Enumeration Number Theory Primality Test Sieve Theory Prime Number Sieve

#42

Rank

#2507EasyFrequency: 16.4%

Number of Common Factors

Math Enumeration Number Theory Euclidean Algorithm Greatest Common Divisor

#43

Rank

#3583HardFrequency: 16.4%

Sorted GCD Pair Queries

Array Hash Table Math Binary Search Combinatorics Counting Number Theory Prefix Sum Euclidean Algorithm Greatest Common Divisor

#44

Rank

#2753MediumFrequency: 16.4%

Minimum Number of Operations to Make All Array Elements Equal to 1

Array Math Number Theory Euclidean Algorithm Greatest Common Divisor

#45

Rank

#4085MediumFrequency: 16.4%

Largest Prime from Consecutive Prime Sum

#46

Rank

#3995EasyFrequency: 16.4%

GCD of Odd and Even Sums

#47

Rank

#2106EasyFrequency: 14.6%

Find Greatest Common Divisor of Array

Array Math Number Theory Euclidean Algorithm Greatest Common Divisor

#48

Rank

#2709MediumFrequency: 14.6%

Count the Number of Square-Free Subsets

Array Math Dynamic Programming Bit Manipulation Number Theory Bitmask

#49

Rank

#3635HardFrequency: 12.6%

Smallest Divisible Digit Product II

Math String Backtracking Greedy Number Theory

#50

Rank

#2903MediumFrequency: 12%

Insert Greatest Common Divisors in Linked List

Linked List Math Number Theory

#51

Rank

#3001HardFrequency: 10.5%

Apply Operations to Maximize Score

Array Math Stack Greedy Sorting Monotonic Stack Number Theory

#52

Rank

#888MediumFrequency: 10.3%

Mirror Reflection

Math Geometry Number Theory Least Common Multiple Greatest Common Divisor

#53

Rank

#2129MediumFrequency: 10.3%

Number of Pairs of Interchangeable Rectangles

Array Hash Table Math Counting Number Theory

#54

Rank

#1372HardFrequency: 8.1%

Check If It Is a Good Array

Array Math Number Theory Bézout's Lemma Euclidean Algorithm Greatest Common Divisor Extended Euclidean Algorithm

#55

Rank

#3702EasyFrequency: 8.1%

Maximum Subarray With Equal Products

Array Math Sliding Window Enumeration Number Theory

#56

Rank

#3507MediumFrequency: 7.3%

Find the Count of Numbers Which Are Not Special

#57

Rank

#1307MediumFrequency: 7.2%

Ugly Number III

Math Binary Search Combinatorics Number Theory Least Common Multiple Euclidean Algorithm Greatest Common Divisor Inclusion-Exclusion Principle

#58

Rank

#4277MediumFrequency: 5.5%

Minimum Operations to Transform Array into Alternating Prime

Array Math Two Pointers Binary Search Sorting Number Theory

#59

Rank

#3552HardFrequency: 5%

Find the Largest Palindrome Divisible by K

Math String Dynamic Programming Greedy Number Theory

#60

Rank

#2609MediumFrequency: 5%

Distinct Prime Factors of Product of Array

Array Hash Table Math Number Theory Prime Factorization Euclidean Algorithm Primality Test Greatest Common Divisor Sieve Theory Prime Number Sieve

#61

Rank

#3607MediumFrequency: 5%

Minimum Division Operations to Make Array Non Decreasing

#62

Rank

#2722EasyFrequency: 5%

Prime In Diagonal

Array Math Matrix Number Theory

#63

Rank

#3907MediumFrequency: 5%

Count Prime-Gap Balanced Subarrays

Array Math Queue Sliding Window Number Theory Monotonic Queue

#64

Rank

#3774HardFrequency: 5%

Check If Digits Are Equal in String After Operations II

Math String Combinatorics Number Theory

#65

Rank

#3947MediumFrequency: 5%

Balanced K-Factor Decomposition

Math Backtracking Number Theory

#66

Rank

#3957HardFrequency: 5%

Sum of Perfect Square Ancestors

Array Hash Table Math Tree Depth-First Search Counting Number Theory

#67

Rank

#2557MediumFrequency: 5%

Number of Subarrays With LCM Equal to K

#68

Rank

#3878HardFrequency: 5%

Maximize Count of Distinct Primes After Split

Array Hash Table Math Segment Tree Number Theory Ordered Set

#69

Rank

#2628MediumFrequency: 5%

Minimize the Maximum of Two Arrays

Math Binary Search Number Theory Least Common Multiple Inclusion-Exclusion Principle

#70

Rank

#2670MediumFrequency: 5%

Make K-Subarray Sums Equal

Array Math Greedy Sorting Number Theory

#71

Rank

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Number Theory Interview Questions

Master 71 number theory problems frequently asked in technical interviews. These questions test your understanding of number theoryconcepts and are essential for coding interview success.

Total Problems

Easy

Medium

Hard

Find the Number of Subsequences With Equal GCD

Array Math Dynamic Programming Number Theory Euclidean Algorithm Greatest Common Divisor

Rank

#2301HardFrequency: 73.2%

Count Array Pairs Divisible by K

Asked at PayPal

Array Hash Table Math Counting Number Theory Euclidean Algorithm Greatest Common Divisor

Rank

#2415HardFrequency: 67.6%

Count the Number of Ideal Arrays

Math Dynamic Programming Combinatorics Number Theory Prime Factorization Fermat's Little Theorem

Rank

#4215HardFrequency: 67.6%

Good Subsequence Queries

Array Math Segment Tree Number Theory

Rank

#3989HardFrequency: 62.5%

Sum of Beautiful Subsequences

Array Math Binary Indexed Tree Number Theory

Rank

#3294MediumFrequency: 55.1%

Number of Self-Divisible Permutations

Asked at Salesforce

Array Math Dynamic Programming Backtracking Bit Manipulation Number Theory Bitmask

Rank

#2610MediumFrequency: 54.4%

Closest Prime Numbers in Range

Asked at TikTok

Math Number Theory Primality Test Sieve Theory Prime Number Sieve

Rank

#3244MediumFrequency: 53.4%

Minimize Length of Array Using Operations

Asked at Oracle

Rank

#204MediumFrequency: 47.3%

Count Primes

Array Math Enumeration Number Theory Primality Test Sieve Theory Prime Number Sieve

Rank

#2423HardFrequency: 44.7%

Minimum Deletions to Make Array Divisible

Array Math Sorting Heap (Priority Queue)Number Theory Euclidean Algorithm Greatest Common Divisor

#10

Rank

#4065HardFrequency: 44.7%

Count Sequences to K

Array Math Dynamic Programming Memoization Number Theory

#11

Rank

#1585MediumFrequency: 43.6%

The kth Factor of n

Math Number Theory Prime Factorization

#12

Rank

#258EasyFrequency: 43.3%

Add Digits

Math Simulation Number Theory

#13

Rank

#2324MediumFrequency: 40.8%

Find Triangular Sum of an Array

Array Math Simulation Combinatorics Number Theory

#14

Rank

#3949MediumFrequency: 35.1%

Minimum Number of Primes to Sum to Target

Array Math Dynamic Programming Number Theory

#15

Rank

#2307HardFrequency: 33.5%

Replace Non-Coprime Numbers in Array

Array Math Stack Number Theory Least Common Multiple Greatest Common Divisor

#16

Rank

#3273MediumFrequency: 33.3%

Most Expensive Item That Can Not Be Bought

Math Dynamic Programming Number Theory

#17

Rank

#3655MediumFrequency: 32.8%

Digit Operations to Make Two Integers Equal

Math Graph Theory Heap (Priority Queue)Number Theory Shortest Path

#18

Rank

#1947HardFrequency: 31.3%

Number of Different Subsequences GCDs

Array Math Counting Number Theory Euclidean Algorithm Greatest Common Divisor

#19

Rank

#4242MediumFrequency: 29.1%

Sum of GCD of Formed Pairs

Array Math Two Pointers Sorting Simulation Number Theory

#20

Rank

#1223HardFrequency: 27.8%

Graph Connectivity With Threshold

Array Math Union-Find Number Theory

#21

Rank

#3933MediumFrequency: 27.8%

Minimum Jumps to Reach End via Prime Teleportation

Array Hash Table Math Breadth-First Search Number Theory

#22

Rank

#1936HardFrequency: 27.3%

Maximize Number of Nice Divisors

Math Recursion Number Theory

#23

Rank

#2083EasyFrequency: 27.3%

Three Divisors

Math Enumeration Number Theory Prime Factorization Sieve Theory

#24

Rank

#2125HardFrequency: 26.5%

GCD Sort of an Array

Array Math Union-Find Sorting Number Theory Prime Factorization Euclidean Algorithm Greatest Common Divisor

#25

Rank

#3768EasyFrequency: 26.5%

Check If Digits Are Equal in String After Operations I

Math String Simulation Combinatorics Number Theory

#26

Rank

#950EasyFrequency: 24.4%

X of a Kind in a Deck of Cards

Array Hash Table Math Counting Number Theory Euclidean Algorithm Greatest Common Divisor

#27

Rank

#3210MediumFrequency: 23.6%

Count Beautiful Substrings I

Hash Table Math String Enumeration Number Theory Prefix Sum

#28

Rank

#3920HardFrequency: 23.6%

Minimum Stability Factor of Array

Array Math Binary Search Greedy Segment Tree Number Theory

#29

Rank

#4301MediumFrequency: 23.6%

Minimize Array Sum Using Divisible Replacements

Array Hash Table Math Greedy Number Theory

#30

Rank

#989HardFrequency: 22.1%

Largest Component Size by Common Factor

Array Hash Table Math Union-Find Number Theory Prime Factorization

#31

Rank

#3888HardFrequency: 20.9%

Maximize Subarray GCD Score

Array Math Enumeration Number Theory

#32

Rank

#897MediumFrequency: 20.3%

Prime Palindrome

Math Number Theory Primality Test

#33

Rank

#1836HardFrequency: 20%

Count Ways to Make Array With Product

Array Math Dynamic Programming Combinatorics Number Theory Prime Factorization Fermat's Little Theorem

#34

Rank

#3208HardFrequency: 20%

Count Beautiful Substrings II

Hash Table Math String Number Theory Prefix Sum

#35

Rank

#2716MediumFrequency: 19.5%

Prime Subtraction Operation

Array Math Binary Search Greedy Number Theory

#36

Rank

#1543MediumFrequency: 18%

Simplified Fractions

Math String Number Theory Euclidean Algorithm Greatest Common Divisor

#37

Rank

#1728HardFrequency: 18%

Fancy Sequence

Math Design Segment Tree Number Theory Fermat's Little Theorem

#38

Rank

#2491EasyFrequency: 18%

Smallest Even Multiple

#39

Rank

#1875HardFrequency: 16.4%

Tree of Coprimes

Array Math Tree Depth-First Search Number Theory

#40

Rank

#2367MediumFrequency: 16.4%

Minimum Lines to Represent a Line Chart

Array Math Geometry Sorting Number Theory

#41

Rank

#3314MediumFrequency: 16.4%

Most Frequent Prime

Array Hash Table Math Matrix Counting Enumeration Number Theory Primality Test Sieve Theory Prime Number Sieve

#42

Rank

#2507EasyFrequency: 16.4%

Number of Common Factors

Math Enumeration Number Theory Euclidean Algorithm Greatest Common Divisor

#43

Rank

#3583HardFrequency: 16.4%

Sorted GCD Pair Queries

Array Hash Table Math Binary Search Combinatorics Counting Number Theory Prefix Sum Euclidean Algorithm Greatest Common Divisor

#44

Rank

#2753MediumFrequency: 16.4%

Minimum Number of Operations to Make All Array Elements Equal to 1

Array Math Number Theory Euclidean Algorithm Greatest Common Divisor

#45

Rank

#4085MediumFrequency: 16.4%

Largest Prime from Consecutive Prime Sum

#46

Rank

#3995EasyFrequency: 16.4%

GCD of Odd and Even Sums

#47

Rank

#2106EasyFrequency: 14.6%

Find Greatest Common Divisor of Array

Array Math Number Theory Euclidean Algorithm Greatest Common Divisor

#48

Rank

#2709MediumFrequency: 14.6%

Count the Number of Square-Free Subsets

Array Math Dynamic Programming Bit Manipulation Number Theory Bitmask

#49

Rank

#3635HardFrequency: 12.6%

Smallest Divisible Digit Product II

Math String Backtracking Greedy Number Theory

#50

Rank

#2903MediumFrequency: 12%

Insert Greatest Common Divisors in Linked List

Linked List Math Number Theory

#51

Rank

#3001HardFrequency: 10.5%

Apply Operations to Maximize Score

Array Math Stack Greedy Sorting Monotonic Stack Number Theory

#52

Rank

#888MediumFrequency: 10.3%

Mirror Reflection

Math Geometry Number Theory Least Common Multiple Greatest Common Divisor

#53

Rank

#2129MediumFrequency: 10.3%

Number of Pairs of Interchangeable Rectangles

Array Hash Table Math Counting Number Theory

#54

Rank

#1372HardFrequency: 8.1%

Check If It Is a Good Array

Array Math Number Theory Bézout's Lemma Euclidean Algorithm Greatest Common Divisor Extended Euclidean Algorithm

#55

Rank

#3702EasyFrequency: 8.1%

Maximum Subarray With Equal Products

Array Math Sliding Window Enumeration Number Theory

#56

Rank

#3507MediumFrequency: 7.3%

Find the Count of Numbers Which Are Not Special

#57

Rank

#1307MediumFrequency: 7.2%

Ugly Number III

Math Binary Search Combinatorics Number Theory Least Common Multiple Euclidean Algorithm Greatest Common Divisor Inclusion-Exclusion Principle

#58

Rank

#4277MediumFrequency: 5.5%

Minimum Operations to Transform Array into Alternating Prime

Array Math Two Pointers Binary Search Sorting Number Theory

#59

Rank

#3552HardFrequency: 5%

Find the Largest Palindrome Divisible by K

Math String Dynamic Programming Greedy Number Theory

#60

Rank

#2609MediumFrequency: 5%

Distinct Prime Factors of Product of Array

Array Hash Table Math Number Theory Prime Factorization Euclidean Algorithm Primality Test Greatest Common Divisor Sieve Theory Prime Number Sieve

#61

Rank

#3607MediumFrequency: 5%

Minimum Division Operations to Make Array Non Decreasing

#62

Rank

#2722EasyFrequency: 5%

Prime In Diagonal

Array Math Matrix Number Theory

#63

Rank

#3907MediumFrequency: 5%

Count Prime-Gap Balanced Subarrays

Array Math Queue Sliding Window Number Theory Monotonic Queue

#64

Rank

#3774HardFrequency: 5%

Check If Digits Are Equal in String After Operations II

Math String Combinatorics Number Theory

#65

Rank

#3947MediumFrequency: 5%

Balanced K-Factor Decomposition

Math Backtracking Number Theory

#66

Rank

#3957HardFrequency: 5%

Sum of Perfect Square Ancestors

Array Hash Table Math Tree Depth-First Search Counting Number Theory

#67

Rank

#2557MediumFrequency: 5%

Number of Subarrays With LCM Equal to K

#68

Rank

#3878HardFrequency: 5%

Maximize Count of Distinct Primes After Split

Array Hash Table Math Segment Tree Number Theory Ordered Set

#69

Rank

#2628MediumFrequency: 5%

Minimize the Maximum of Two Arrays

Math Binary Search Number Theory Least Common Multiple Inclusion-Exclusion Principle

#70

Rank

#2670MediumFrequency: 5%

Make K-Subarray Sums Equal