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Problems Archives

  • Problem 709 will be accessible in 4 hours, 37 minutes (Saturday, 4th April 2020, 05:00 pm)

The problems archives table shows problems 1 to 698. 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
932612
2Even Fibonacci numbers
742571
3Largest prime factor
530936
4Largest palindrome product
469080
5Smallest multiple
473643
6Sum square difference
476684
710001st prime
406983
8Largest product in a series
339861
9Special Pythagorean triplet
345232
10Summation of primes
315723
11Largest product in a grid
225644
12Highly divisible triangular number
212341
13Large sum
217792
14Longest Collatz sequence
218052
15Lattice paths
179526
16Power digit sum
220330
17Number letter counts
145081
18Maximum path sum I
138906
19Counting Sundays
129190
20Factorial digit sum
190818
21Amicable numbers
140123
22Names scores
128543
23Non-abundant sums
99213
24Lexicographic permutations
109628
251000-digit Fibonacci number
149206
26Reciprocal cycles
79791
27Quadratic primes
83102
28Number spiral diagonals
103641
29Distinct powers
100565
30Digit fifth powers
105167
31Coin sums
80863
32Pandigital products
67534
33Digit cancelling fractions
68066
34Digit factorials
89956
35Circular primes
80714
36Double-base palindromes
84793
37Truncatable primes
69902
38Pandigital multiples
59665
39Integer right triangles
69458
40Champernowne's constant
76251
41Pandigital prime
64541
42Coded triangle numbers
70771
43Sub-string divisibility
56495
44Pentagon numbers
55205
45Triangular, pentagonal, and hexagonal
67565
46Goldbach's other conjecture
58207
47Distinct primes factors
54793
48Self powers
107841
49Prime permutations
54716
50Consecutive prime sum
59168