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Problems Archives

  • Problem 639 will be accessible in 1 hour, 2 minutes (Sunday, 21st October 2018, 07:00 am)

The problems archives table shows problems 1 to 628. 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
790853
2Even Fibonacci numbers
633765
3Largest prime factor
453321
4Largest palindrome product
402808
5Smallest multiple
410533
6Sum square difference
412983
710001st prime
353343
8Largest product in a series
297565
9Special Pythagorean triplet
300916
10Summation of primes
275833
11Largest product in a grid
199351
12Highly divisible triangular number
186660
13Large sum
192171
14Longest Collatz sequence
191953
15Lattice paths
158481
16Power digit sum
194046
17Number letter counts
128818
18Maximum path sum I
123706
19Counting Sundays
114975
20Factorial digit sum
169592
21Amicable numbers
124217
22Names scores
114660
23Non-abundant sums
88143
24Lexicographic permutations
97845
251000-digit Fibonacci number
132495
26Reciprocal cycles
71011
27Quadratic primes
74166
28Number spiral diagonals
93048
29Distinct powers
89229
30Digit fifth powers
93446
31Coin sums
71566
32Pandigital products
60252
33Digit cancelling fractions
60949
34Digit factorials
80203
35Circular primes
72353
36Double-base palindromes
76192
37Truncatable primes
62635
38Pandigital multiples
53350
39Integer right triangles
62093
40Champernowne's constant
68323
41Pandigital prime
57812
42Coded triangle numbers
63711
43Sub-string divisibility
50462
44Pentagon numbers
49031
45Triangular, pentagonal, and hexagonal
60715
46Goldbach's other conjecture
51877
47Distinct primes factors
48970
48Self powers
97161
49Prime permutations
48997
50Consecutive prime sum
52735