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Problems Archives

The problems archives table shows problems 1 to 624. If you would like to tackle the 10 most recently published problems then go to Recent problems.
Click the description/title of the problem to view details and submit your answer.


IDDescription / TitleSolved By
1Multiples of 3 and 5
773284
2Even Fibonacci numbers
620673
3Largest prime factor
444246
4Largest palindrome product
395172
5Smallest multiple
403097
6Sum square difference
405512
710001st prime
347019
8Largest product in a series
292728
9Special Pythagorean triplet
295861
10Summation of primes
271319
11Largest product in a grid
196405
12Highly divisible triangular number
183741
13Large sum
189346
14Longest Collatz sequence
188983
15Lattice paths
156168
16Power digit sum
191057
17Number letter counts
127002
18Maximum path sum I
122022
19Counting Sundays
113427
20Factorial digit sum
167249
21Amicable numbers
122519
22Names scores
113034
23Non-abundant sums
86946
24Lexicographic permutations
96569
251000-digit Fibonacci number
130645
26Reciprocal cycles
70059
27Quadratic primes
73225
28Number spiral diagonals
91954
29Distinct powers
88043
30Digit fifth powers
92243
31Coin sums
70618
32Pandigital products
59494
33Digit cancelling fractions
60205
34Digit factorials
79194
35Circular primes
71451
36Double-base palindromes
75266
37Truncatable primes
61841
38Pandigital multiples
52671
39Integer right triangles
61294
40Champernowne's constant
67476
41Pandigital prime
57054
42Coded triangle numbers
62959
43Sub-string divisibility
49792
44Pentagon numbers
48377
45Triangular, pentagonal, and hexagonal
59947
46Goldbach's other conjecture
51175
47Distinct primes factors
48326
48Self powers
95947
49Prime permutations
48328
50Consecutive prime sum
52027