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Problems Archives

  • Problem 699 will be accessible in 3 hours, 55 minutes (Sunday, 26th January 2020, 10:00 am)

The problems archives table shows problems 1 to 688. 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
913830
2Even Fibonacci numbers
727981
3Largest prime factor
520309
4Largest palindrome product
459872
5Smallest multiple
464928
6Sum square difference
467992
710001st prime
399602
8Largest product in a series
333961
9Special Pythagorean triplet
339148
10Summation of primes
310252
11Largest product in a grid
222009
12Highly divisible triangular number
208766
13Large sum
214271
14Longest Collatz sequence
214453
15Lattice paths
176621
16Power digit sum
216670
17Number letter counts
142875
18Maximum path sum I
136825
19Counting Sundays
127275
20Factorial digit sum
187918
21Amicable numbers
137935
22Names scores
126665
23Non-abundant sums
97670
24Lexicographic permutations
108031
251000-digit Fibonacci number
146992
26Reciprocal cycles
78659
27Quadratic primes
81907
28Number spiral diagonals
102285
29Distinct powers
99106
30Digit fifth powers
103679
31Coin sums
79663
32Pandigital products
66551
33Digit cancelling fractions
67129
34Digit factorials
88689
35Circular primes
79603
36Double-base palindromes
83648
37Truncatable primes
68945
38Pandigital multiples
58851
39Integer right triangles
68489
40Champernowne's constant
75223
41Pandigital prime
63630
42Coded triangle numbers
69847
43Sub-string divisibility
55662
44Pentagon numbers
54399
45Triangular, pentagonal, and hexagonal
66691
46Goldbach's other conjecture
57390
47Distinct primes factors
54067
48Self powers
106455
49Prime permutations
53956
50Consecutive prime sum
58279