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Problems Archives

The problems archives table shows problems 1 to 636. 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
804921
2Even Fibonacci numbers
644409
3Largest prime factor
460692
4Largest palindrome product
408825
5Smallest multiple
416380
6Sum square difference
418934
710001st prime
358297
8Largest product in a series
301379
9Special Pythagorean triplet
305142
10Summation of primes
279467
11Largest product in a grid
201767
12Highly divisible triangular number
189026
13Large sum
194494
14Longest Collatz sequence
194288
15Lattice paths
160593
16Power digit sum
196467
17Number letter counts
130328
18Maximum path sum I
125098
19Counting Sundays
116379
20Factorial digit sum
171535
21Amicable numbers
125646
22Names scores
115900
23Non-abundant sums
89162
24Lexicographic permutations
99057
251000-digit Fibonacci number
134177
26Reciprocal cycles
71855
27Quadratic primes
74992
28Number spiral diagonals
94163
29Distinct powers
90263
30Digit fifth powers
94512
31Coin sums
72601
32Pandigital products
60938
33Digit cancelling fractions
61628
34Digit factorials
81141
35Circular primes
73130
36Double-base palindromes
76990
37Truncatable primes
63279
38Pandigital multiples
53956
39Integer right triangles
62793
40Champernowne's constant
69063
41Pandigital prime
58477
42Coded triangle numbers
64401
43Sub-string divisibility
51027
44Pentagon numbers
49602
45Triangular, pentagonal, and hexagonal
61350
46Goldbach's other conjecture
52458
47Distinct primes factors
49489
48Self powers
98155
49Prime permutations
49536
50Consecutive prime sum
53328