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Problems Archives

The problems archives table shows problems 1 to 713. 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.


ID

Description / TitleSolved By
1Multiples of 3 and 5
963996
2Even Fibonacci numbers
766992
3Largest prime factor
549390
4Largest palindrome product
485158
5Smallest multiple
488784
6Sum square difference
491814
710001st prime
420117
8Largest product in a series
350785
9Special Pythagorean triplet
356296
10Summation of primes
325952
11Largest product in a grid
232715
12Highly divisible triangular number
219455
13Large sum
224631
14Longest Collatz sequence
224983
15Lattice paths
185219
16Power digit sum
227349
17Number letter counts
149757
18Maximum path sum I
143244
19Counting Sundays
133129
20Factorial digit sum
196593
21Amicable numbers
144591
22Names scores
132561
23Non-abundant sums
102408
24Lexicographic permutations
113021
251000-digit Fibonacci number
153657
26Reciprocal cycles
82356
27Quadratic primes
85733
28Number spiral diagonals
106552
29Distinct powers
103771
30Digit fifth powers
108406
31Coin sums
83495
32Pandigital products
69750
33Digit cancelling fractions
70208
34Digit factorials
92715
35Circular primes
83099
36Double-base palindromes
87255
37Truncatable primes
72070
38Pandigital multiples
61563
39Integer right triangles
71655
40Champernowne's constant
78512
41Pandigital prime
66602
42Coded triangle numbers
72882
43Sub-string divisibility
58318
44Pentagon numbers
57003
45Triangular, pentagonal, and hexagonal
69537
46Goldbach's other conjecture
60076
47Distinct primes factors
56499
48Self powers
110617
49Prime permutations
56403
50Consecutive prime sum
60986