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Problems Archives

The problems archives table shows problems 1 to 629. 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
791208
2Even Fibonacci numbers
634024
3Largest prime factor
453503
4Largest palindrome product
402966
5Smallest multiple
410694
6Sum square difference
413147
710001st prime
353453
8Largest product in a series
297651
9Special Pythagorean triplet
301019
10Summation of primes
275929
11Largest product in a grid
199419
12Highly divisible triangular number
186701
13Large sum
192205
14Longest Collatz sequence
192009
15Lattice paths
158529
16Power digit sum
194102
17Number letter counts
128864
18Maximum path sum I
123740
19Counting Sundays
115009
20Factorial digit sum
169643
21Amicable numbers
124243
22Names scores
114681
23Non-abundant sums
88168
24Lexicographic permutations
97868
251000-digit Fibonacci number
132532
26Reciprocal cycles
71028
27Quadratic primes
74188
28Number spiral diagonals
93079
29Distinct powers
89261
30Digit fifth powers
93481
31Coin sums
71595
32Pandigital products
60268
33Digit cancelling fractions
60973
34Digit factorials
80226
35Circular primes
72369
36Double-base palindromes
76210
37Truncatable primes
62647
38Pandigital multiples
53369
39Integer right triangles
62120
40Champernowne's constant
68340
41Pandigital prime
57834
42Coded triangle numbers
63726
43Sub-string divisibility
50479
44Pentagon numbers
49045
45Triangular, pentagonal, and hexagonal
60726
46Goldbach's other conjecture
51887
47Distinct primes factors
48982
48Self powers
97180
49Prime permutations
49007
50Consecutive prime sum
52747