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Problems Archives

The problems archives table shows problems 1 to 564. 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
604956
2Even Fibonacci numbers
491358
3Largest prime factor
354014
4Largest palindrome product
317418
5Smallest multiple
328070
6Sum square difference
330050
710001st prime
282733
8Largest product in a series
241541
9Special Pythagorean triplet
242582
10Summation of primes
222855
11Largest product in a grid
163344
12Highly divisible triangular number
151236
13Large sum
157260
14Longest Collatz sequence
155860
15Lattice paths
129357
16Power digit sum
159143
17Number letter counts
106074
18Maximum path sum I
102486
19Counting Sundays
94972
20Factorial digit sum
141225
21Amicable numbers
102146
22Names scores
94687
23Non-abundant sums
72354
24Lexicographic permutations
81147
251000-digit Fibonacci number
109685
26Reciprocal cycles
58662
27Quadratic primes
61485
28Number spiral diagonals
78265
29Distinct powers
73720
30Digit fifth powers
77431
31Coin sums
58759
32Pandigital products
49876
33Digit cancelling fractions
50759
34Digit factorials
66867
35Circular primes
60570
36Double-base palindromes
63927
37Truncatable primes
52081
38Pandigital multiples
44331
39Integer right triangles
51421
40Champernowne's constant
56986
41Pandigital prime
47959
42Coded triangle numbers
53549
43Sub-string divisibility
41572
44Pentagon numbers
40260
45Triangular, pentagonal, and hexagonal
50851
46Goldbach's other conjecture
42673
47Distinct primes factors
40489
48Self powers
82281
49Prime permutations
40431
50Consecutive prime sum
43404