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Problems Archives

The problems archives table shows problems 1 to 641. 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
815460
2Even Fibonacci numbers
652543
3Largest prime factor
466406
4Largest palindrome product
413695
5Smallest multiple
421054
6Sum square difference
423603
710001st prime
362244
8Largest product in a series
304515
9Special Pythagorean triplet
308376
10Summation of primes
282342
11Largest product in a grid
203771
12Highly divisible triangular number
190984
13Large sum
196372
14Longest Collatz sequence
196219
15Lattice paths
162103
16Power digit sum
198304
17Number letter counts
131481
18Maximum path sum I
126179
19Counting Sundays
117397
20Factorial digit sum
173010
21Amicable numbers
126837
22Names scores
116902
23Non-abundant sums
89984
24Lexicographic permutations
99886
251000-digit Fibonacci number
135321
26Reciprocal cycles
72570
27Quadratic primes
75670
28Number spiral diagonals
94999
29Distinct powers
91075
30Digit fifth powers
95428
31Coin sums
73308
32Pandigital products
61467
33Digit cancelling fractions
62130
34Digit factorials
81877
35Circular primes
73720
36Double-base palindromes
77619
37Truncatable primes
63783
38Pandigital multiples
54376
39Integer right triangles
63311
40Champernowne's constant
69606
41Pandigital prime
58944
42Coded triangle numbers
64857
43Sub-string divisibility
51448
44Pentagon numbers
50028
45Triangular, pentagonal, and hexagonal
61852
46Goldbach's other conjecture
52880
47Distinct primes factors
49893
48Self powers
98943
49Prime permutations
49933
50Consecutive prime sum
53786