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Problems Archives

The problems archives table shows problems 1 to 499. 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
449014
2Even Fibonacci numbers
368968
3Largest prime factor
268424
4Largest palindrome product
242880
5Smallest multiple
255653
6Sum square difference
257470
710001st prime
220692
8Largest product in a series
192386
9Special Pythagorean triplet
191524
10Summation of primes
175806
11Largest product in a grid
130754
12Highly divisible triangular number
119391
13Large sum
125928
14Longest Collatz sequence
123907
15Lattice paths
103291
16Power digit sum
128529
17Number letter counts
84990
18Maximum path sum I
82757
19Counting Sundays
76554
20Factorial digit sum
115933
21Amicable numbers
82233
22Names scores
76663
23Non-abundant sums
57968
24Lexicographic permutations
66015
251000-digit Fibonacci number
89451
26Reciprocal cycles
47259
27Quadratic primes
49749
28Number spiral diagonals
64962
29Distinct powers
59735
30Digit fifth powers
63232
31Coin sums
47260
32Pandigital products
40427
33Digit cancelling fractions
41497
34Digit factorials
54949
35Circular primes
50083
36Double-base palindromes
53058
37Truncatable primes
42593
38Pandigital multiples
36221
39Integer right triangles
42009
40Champernowne's constant
46797
41Pandigital prime
39198
42Coded triangle numbers
44502
43Sub-string divisibility
33665
44Pentagon numbers
32424
45Triangular, pentagonal, and hexagonal
42214
46Goldbach's other conjecture
34580
47Distinct primes factors
32936
48Self powers
69663
49Prime permutations
32796
50Consecutive prime sum
35160