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Problems Archives

The problems archives table shows problems 1 to 565. 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
606731
2Even Fibonacci numbers
492699
3Largest prime factor
354978
4Largest palindrome product
318160
5Smallest multiple
328856
6Sum square difference
330775
710001st prime
283393
8Largest product in a series
242035
9Special Pythagorean triplet
243082
10Summation of primes
223350
11Largest product in a grid
163681
12Highly divisible triangular number
151563
13Large sum
157557
14Longest Collatz sequence
156155
15Lattice paths
129615
16Power digit sum
159440
17Number letter counts
106246
18Maximum path sum I
102670
19Counting Sundays
95149
20Factorial digit sum
141473
21Amicable numbers
102362
22Names scores
94846
23Non-abundant sums
72499
24Lexicographic permutations
81296
251000-digit Fibonacci number
109875
26Reciprocal cycles
58775
27Quadratic primes
61599
28Number spiral diagonals
78396
29Distinct powers
73843
30Digit fifth powers
77573
31Coin sums
58873
32Pandigital products
49968
33Digit cancelling fractions
50850
34Digit factorials
66981
35Circular primes
60672
36Double-base palindromes
64013
37Truncatable primes
52160
38Pandigital multiples
44396
39Integer right triangles
51497
40Champernowne's constant
57078
41Pandigital prime
48029
42Coded triangle numbers
53616
43Sub-string divisibility
41630
44Pentagon numbers
40328
45Triangular, pentagonal, and hexagonal
50916
46Goldbach's other conjecture
42751
47Distinct primes factors
40572
48Self powers
82410
49Prime permutations
40504
50Consecutive prime sum
43498