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Problems Archives

The problems archives table shows problems 1 to 666. 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
858935
2Even Fibonacci numbers
686044
3Largest prime factor
490207
4Largest palindrome product
434217
5Smallest multiple
440355
6Sum square difference
443181
710001st prime
378836
8Largest product in a series
317249
9Special Pythagorean triplet
321945
10Summation of primes
294709
11Largest product in a grid
211764
12Highly divisible triangular number
198698
13Large sum
204185
14Longest Collatz sequence
204037
15Lattice paths
168397
16Power digit sum
206263
17Number letter counts
136406
18Maximum path sum I
130822
19Counting Sundays
121615
20Factorial digit sum
179494
21Amicable numbers
131602
22Names scores
121117
23Non-abundant sums
93229
24Lexicographic permutations
103316
251000-digit Fibonacci number
140316
26Reciprocal cycles
75150
27Quadratic primes
78288
28Number spiral diagonals
98035
29Distinct powers
94430
30Digit fifth powers
98936
31Coin sums
75944
32Pandigital products
63623
33Digit cancelling fractions
64234
34Digit factorials
84752
35Circular primes
76140
36Double-base palindromes
80173
37Truncatable primes
65959
38Pandigital multiples
56257
39Integer right triangles
65440
40Champernowne's constant
71954
41Pandigital prime
60899
42Coded triangle numbers
66964
43Sub-string divisibility
53210
44Pentagon numbers
51890
45Triangular, pentagonal, and hexagonal
63900
46Goldbach's other conjecture
54793
47Distinct primes factors
51657
48Self powers
102184
49Prime permutations
51636
50Consecutive prime sum
55698