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Problems Archives

The problems archives table shows problems 1 to 507. 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
464320
2Even Fibonacci numbers
381123
3Largest prime factor
277085
4Largest palindrome product
250479
5Smallest multiple
263017
6Sum square difference
264840
710001st prime
227018
8Largest product in a series
197424
9Special Pythagorean triplet
196775
10Summation of primes
180664
11Largest product in a grid
134163
12Highly divisible triangular number
122697
13Large sum
129218
14Longest Collatz sequence
127283
15Lattice paths
106113
16Power digit sum
131728
17Number letter counts
87215
18Maximum path sum I
84915
19Counting Sundays
78499
20Factorial digit sum
118585
21Amicable numbers
84352
22Names scores
78609
23Non-abundant sums
59526
24Lexicographic permutations
67596
251000-digit Fibonacci number
91543
26Reciprocal cycles
48543
27Quadratic primes
51022
28Number spiral diagonals
66388
29Distinct powers
61203
30Digit fifth powers
64731
31Coin sums
48493
32Pandigital products
41447
33Digit cancelling fractions
42500
34Digit factorials
56189
35Circular primes
51188
36Double-base palindromes
54195
37Truncatable primes
43636
38Pandigital multiples
37072
39Integer right triangles
42990
40Champernowne's constant
47835
41Pandigital prime
40131
42Coded triangle numbers
45454
43Sub-string divisibility
34492
44Pentagon numbers
33276
45Triangular, pentagonal, and hexagonal
43122
46Goldbach's other conjecture
35415
47Distinct primes factors
33752
48Self powers
71007
49Prime permutations
33606
50Consecutive prime sum
36069