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Problems Archives

The problems archives table shows problems 1 to 512. 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
489939
2Even Fibonacci numbers
401531
3Largest prime factor
291475
4Largest palindrome product
263150
5Smallest multiple
275193
6Sum square difference
277056
710001st prime
237511
8Largest product in a series
205845
9Special Pythagorean triplet
205484
10Summation of primes
188672
11Largest product in a grid
139808
12Highly divisible triangular number
128158
13Large sum
134581
14Longest Collatz sequence
132727
15Lattice paths
110538
16Power digit sum
136891
17Number letter counts
90859
18Maximum path sum I
88352
19Counting Sundays
81626
20Factorial digit sum
122933
21Amicable numbers
87770
22Names scores
81699
23Non-abundant sums
62012
24Lexicographic permutations
70267
251000-digit Fibonacci number
94975
26Reciprocal cycles
50505
27Quadratic primes
53113
28Number spiral diagonals
68672
29Distinct powers
63623
30Digit fifth powers
67230
31Coin sums
50558
32Pandigital products
43178
33Digit cancelling fractions
44185
34Digit factorials
58302
35Circular primes
53111
36Double-base palindromes
56194
37Truncatable primes
45368
38Pandigital multiples
38604
39Integer right triangles
44694
40Champernowne's constant
49647
41Pandigital prime
41698
42Coded triangle numbers
47053
43Sub-string divisibility
35932
44Pentagon numbers
34670
45Triangular, pentagonal, and hexagonal
44678
46Goldbach's other conjecture
36878
47Distinct primes factors
35122
48Self powers
73172
49Prime permutations
34989
50Consecutive prime sum
37529