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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
858937
2Even Fibonacci numbers
686045
3Largest prime factor
490214
4Largest palindrome product
434219
5Smallest multiple
440358
6Sum square difference
443182
710001st prime
378837
8Largest product in a series
317249
9Special Pythagorean triplet
321945
10Summation of primes
294710
11Largest product in a grid
211764
12Highly divisible triangular number
198698
13Large sum
204186
14Longest Collatz sequence
204037
15Lattice paths
168397
16Power digit sum
206263
17Number letter counts
136406
18Maximum path sum I
130824
19Counting Sundays
121615
20Factorial digit sum
179495
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
98036
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
55699