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Problems Archives

The problems archives table shows problems 1 to 563. 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
603967
2Even Fibonacci numbers
490670
3Largest prime factor
353531
4Largest palindrome product
317008
5Smallest multiple
327671
6Sum square difference
329647
710001st prime
282394
8Largest product in a series
241263
9Special Pythagorean triplet
242285
10Summation of primes
222603
11Largest product in a grid
163177
12Highly divisible triangular number
151059
13Large sum
157099
14Longest Collatz sequence
155702
15Lattice paths
129231
16Power digit sum
158987
17Number letter counts
105972
18Maximum path sum I
102391
19Counting Sundays
94869
20Factorial digit sum
141090
21Amicable numbers
102040
22Names scores
94602
23Non-abundant sums
72277
24Lexicographic permutations
81086
251000-digit Fibonacci number
109592
26Reciprocal cycles
58603
27Quadratic primes
61427
28Number spiral diagonals
78192
29Distinct powers
73649
30Digit fifth powers
77357
31Coin sums
58687
32Pandigital products
49831
33Digit cancelling fractions
50719
34Digit factorials
66815
35Circular primes
60528
36Double-base palindromes
63879
37Truncatable primes
52045
38Pandigital multiples
44292
39Integer right triangles
51379
40Champernowne's constant
56942
41Pandigital prime
47913
42Coded triangle numbers
53506
43Sub-string divisibility
41524
44Pentagon numbers
40223
45Triangular, pentagonal, and hexagonal
50813
46Goldbach's other conjecture
42640
47Distinct primes factors
40454
48Self powers
82225
49Prime permutations
40386
50Consecutive prime sum
43370