Number Theory LeetCode Problems: All 54, With Python Solutions
Every problem in this library that LeetCode tags Number Theory — 54 in total, 47 of them with a complete Python solution, a worked example and the time and space complexity of the approach.
- 54 problems
- 8 Easy
- 24 Medium
- 22 Hard
How Number Theory problems are solved
A tag names the subject, not the method. These pattern hubs cover the techniques that actually solve Number Theory problems — each one explains the approach, gives a Python template and states its complexity.
- Math and Number Theory — Find the closed form, the invariant, or the modular identity — and skip the loop entirely.
Number Theory problems by difficulty
Problems with a complete Python solution are listed first, then by ascending problem number.
Easy (8)
| # | Problem | Difficulty | Topics |
|---|---|---|---|
| 258 | Add Digits | Easy | Math, Number Theory, Simulation |
| 914 | X of a Kind in a Deck of Cards | Easy | Array, Hash Table, Math +2 |
| 1952 | Three Divisors | Easy | Math, Enumeration, Number Theory |
| 1979 | Find Greatest Common Divisor of Array | Easy | Array, Math, Number Theory |
| 2413 | Smallest Even Multiple | Easy | Math, Number Theory |
| 2427 | Number of Common Factors | Easy | Math, Enumeration, Number Theory |
| 2614 | Prime In Diagonal | Easy | Array, Math, Matrix +1 |
| 2748 | Number of Beautiful Pairs | Easy | Array, Hash Table, Math +2 |
Medium (24)
| # | Problem | Difficulty | Topics |
|---|---|---|---|
| 204 | Count Primes | Medium | Array, Math, Enumeration +1 |
| 858 | Mirror Reflection | Medium | Geometry, Math, Number Theory |
| 866 | Prime Palindrome | Medium | Math, Number Theory |
| 1201 | Ugly Number III | Medium | Math, Binary Search, Combinatorics +1 |
| 1447 | Simplified Fractions | Medium | Math, String, Number Theory |
| 1492 | The kth Factor of n | Medium | Math, Number Theory |
| 2001 | Number of Pairs of Interchangeable Rectangles | Medium | Array, Hash Table, Math +2 |
| 2280 | Minimum Lines to Represent a Line Chart | Medium | Geometry, Array, Math +2 |
| 2447 | Number of Subarrays With GCD Equal to K | Medium | Array, Math, Number Theory |
| 2470 | Number of Subarrays With LCM Equal to K | Medium | Array, Math, Number Theory |
| 2507 | Smallest Value After Replacing With Sum of Prime Factors | Medium | Math, Number Theory, Simulation |
| 2513 | Minimize the Maximum of Two Arrays | Medium | Math, Binary Search, Number Theory |
| 2521 | Distinct Prime Factors of Product of Array | Medium | Array, Hash Table, Math +1 |
| 2523 | Closest Prime Numbers in Range | Medium | Math, Number Theory |
| 2601 | Prime Subtraction Operation | Medium | Greedy, Array, Math +2 |
| 2607 | Make K-Subarray Sums Equal | Medium | Greedy, Array, Math +2 |
| 2654 | Minimum Number of Operations to Make All Array Elements Equal to 1 | Medium | Array, Math, Number Theory |
| 2761 | Prime Pairs With Target Sum | Medium | Array, Math, Enumeration +1 |
| 2807 | Insert Greatest Common Divisors in Linked List | Medium | Linked List, Math, Number Theory |
| 2947 | Count Beautiful Substrings I | Medium | Hash Table, Math, String +3 |
| 2436 | Minimum Split Into Subarrays With GCD Greater Than OnePremium | Medium | Greedy, Array, Math +2 |
| 2464 | Minimum Subarrays in a Valid SplitPremium | Medium | Array, Math, Dynamic Programming +1 |
| 2979 | Most Expensive Item That Can Not Be BoughtPremium | Medium | Math, Dynamic Programming, Number Theory |
| 2992 | Number of Self-Divisible PermutationsPremium | Medium | Bit Manipulation, Array, Math +4 |
Hard (22)
| # | Problem | Difficulty | Topics |
|---|---|---|---|
| 952 | Largest Component Size by Common Factor | Hard | Union Find, Array, Hash Table +2 |
| 1250 | Check If It Is a Good Array | Hard | Array, Math, Number Theory |
| 1627 | Graph Connectivity With Threshold | Hard | Union Find, Array, Math +1 |
| 1735 | Count Ways to Make Array With Product | Hard | Array, Math, Dynamic Programming +2 |
| 1766 | Tree of Coprimes | Hard | Tree, Depth-First Search, Array +2 |
| 1799 | Maximize Score After N Operations | Hard | Bit Manipulation, Array, Math +4 |
| 1808 | Maximize Number of Nice Divisors | Hard | Recursion, Math, Number Theory |
| 1819 | Number of Different Subsequences GCDs | Hard | Array, Math, Counting +1 |
| 1994 | The Number of Good Subsets | Hard | Bit Manipulation, Array, Hash Table +5 |
| 1998 | GCD Sort of an Array | Hard | Union Find, Array, Math +2 |
| 2197 | Replace Non-Coprime Numbers in Array | Hard | Stack, Array, Math +1 |
| 2338 | Count the Number of Ideal Arrays | Hard | Math, Dynamic Programming, Combinatorics +1 |
| 2344 | Minimum Deletions to Make Array Divisible | Hard | Array, Math, Number Theory +2 |
| 2543 | Check if Point Is Reachable | Hard | Math, Number Theory |
| 2584 | Split the Array to Make Coprime Products | Hard | Array, Hash Table, Math +1 |
| 2709 | Greatest Common Divisor Traversal | Hard | Union Find, Array, Math +1 |
| 2818 | Apply Operations to Maximize Score | Hard | Stack, Greedy, Array +4 |
| 2862 | Maximum Element-Sum of a Complete Subset of Indices | Hard | Array, Math, Number Theory |
| 2867 | Count Valid Paths in a Tree | Hard | Tree, Depth-First Search, Math +2 |
| 2183 | Count Array Pairs Divisible by K | Hard | Array, Math, Number Theory |
| 2941 | Maximum GCD-Sum of a SubarrayPremium | Hard | Array, Math, Binary Search +1 |
| 2949 | Count Beautiful Substrings II | Hard | Hash Table, Math, String +2 |
Keep exploring
All LeetCode topicsEvery tag with a page of its own, with the number of problems behind each.LeetCode patternsThe techniques themselves, with a Python template and complexity for each.Curated study listsBlind 75, NeetCode 150 and three more, grouped by pattern.Easy problemsStart here when the data structure is new rather than the problem.
Other topics
- Array1,569
- String672
- Hash Table588
- Math485
- Dynamic Programming481
- Sorting392
- Greedy346
- Depth-First Search289
- Binary Search253
- Database249
- Tree225
- Breadth-First Search223
- Matrix216
- Two Pointers201
- Bit Manipulation194
- Binary Tree174
- Heap (Priority Queue)163
- Prefix Sum157
- Stack157
- Simulation144
- Graph138
- Counting126
- Design122
- Sliding Window116
When the Number Theory problem arrives live
Stealth Interview is a desktop app for macOS and Windows. It reads the coding problem off your screen, returns a working solution with a step-by-step explanation and its time and space complexity, and transcribes what the interviewer is saying — while staying invisible to screen sharing.