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Problems Archives

  • Problem 666 will be accessible in 1 day, 14 hours, 22 minutes (Saturday, 20th April 2019, 01:00 pm)

The problems archives table shows problems 1 to 655. 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
842723
2Even Fibonacci numbers
673449
3Largest prime factor
481065
4Largest palindrome product
426289
5Smallest multiple
432850
6Sum square difference
435593
710001st prime
372295
8Largest product in a series
312179
9Special Pythagorean triplet
316564
10Summation of primes
289815
11Largest product in a grid
208577
12Highly divisible triangular number
195565
13Large sum
200997
14Longest Collatz sequence
200847
15Lattice paths
165776
16Power digit sum
203003
17Number letter counts
134354
18Maximum path sum I
128877
19Counting Sundays
119838
20Factorial digit sum
176747
21Amicable numbers
129583
22Names scores
119314
23Non-abundant sums
91880
24Lexicographic permutations
101885
251000-digit Fibonacci number
138215
26Reciprocal cycles
74113
27Quadratic primes
77210
28Number spiral diagonals
96731
29Distinct powers
92990
30Digit fifth powers
97431
31Coin sums
74844
32Pandigital products
62707
33Digit cancelling fractions
63348
34Digit factorials
83514
35Circular primes
75121
36Double-base palindromes
79115
37Truncatable primes
65052
38Pandigital multiples
55450
39Integer right triangles
64549
40Champernowne's constant
70981
41Pandigital prime
60103
42Coded triangle numbers
66103
43Sub-string divisibility
52482
44Pentagon numbers
51075
45Triangular, pentagonal, and hexagonal
63028
46Goldbach's other conjecture
53952
47Distinct primes factors
50890
48Self powers
100740
49Prime permutations
50911
50Consecutive prime sum
54865