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Problems Archives

The problems archives table shows problems 1 to 661. 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
850708
2Even Fibonacci numbers
679643
3Largest prime factor
485536
4Largest palindrome product
430211
5Smallest multiple
436489
6Sum square difference
439287
710001st prime
375477
8Largest product in a series
314625
9Special Pythagorean triplet
319206
10Summation of primes
292247
11Largest product in a grid
210155
12Highly divisible triangular number
197108
13Large sum
202603
14Longest Collatz sequence
202438
15Lattice paths
167097
16Power digit sum
204633
17Number letter counts
135376
18Maximum path sum I
129857
19Counting Sundays
120701
20Factorial digit sum
178125
21Amicable numbers
130583
22Names scores
120210
23Non-abundant sums
92550
24Lexicographic permutations
102578
251000-digit Fibonacci number
139250
26Reciprocal cycles
74604
27Quadratic primes
77726
28Number spiral diagonals
97360
29Distinct powers
93697
30Digit fifth powers
98154
31Coin sums
75357
32Pandigital products
63136
33Digit cancelling fractions
63758
34Digit factorials
84108
35Circular primes
75617
36Double-base palindromes
79616
37Truncatable primes
65457
38Pandigital multiples
55814
39Integer right triangles
64979
40Champernowne's constant
71447
41Pandigital prime
60470
42Coded triangle numbers
66526
43Sub-string divisibility
52819
44Pentagon numbers
51440
45Triangular, pentagonal, and hexagonal
63433
46Goldbach's other conjecture
54357
47Distinct primes factors
51263
48Self powers
101442
49Prime permutations
51239
50Consecutive prime sum
55244