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Problems Archives

The problems archives table shows problems 1 to 611. 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
731864
2Even Fibonacci numbers
588973
3Largest prime factor
422033
4Largest palindrome product
376106
5Smallest multiple
384864
6Sum square difference
387105
710001st prime
331370
8Largest product in a series
280391
9Special Pythagorean triplet
282987
10Summation of primes
259678
11Largest product in a grid
188618
12Highly divisible triangular number
176015
13Large sum
181780
14Longest Collatz sequence
181153
15Lattice paths
149810
16Power digit sum
183395
17Number letter counts
122103
18Maximum path sum I
117343
19Counting Sundays
109067
20Factorial digit sum
161050
21Amicable numbers
117550
22Names scores
108668
23Non-abundant sums
83468
24Lexicographic permutations
92842
251000-digit Fibonacci number
125630
26Reciprocal cycles
67375
27Quadratic primes
70495
28Number spiral diagonals
88820
29Distinct powers
84635
30Digit fifth powers
88713
31Coin sums
67764
32Pandigital products
57242
33Digit cancelling fractions
57897
34Digit factorials
76275
35Circular primes
68866
36Double-base palindromes
72494
37Truncatable primes
59483
38Pandigital multiples
50694
39Integer right triangles
58899
40Champernowne's constant
65001
41Pandigital prime
54843
42Coded triangle numbers
60724
43Sub-string divisibility
47785
44Pentagon numbers
46422
45Triangular, pentagonal, and hexagonal
57714
46Goldbach's other conjecture
49118
47Distinct primes factors
46439
48Self powers
92620
49Prime permutations
46425
50Consecutive prime sum
50013