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Problems Archives

The problems archives table shows problems 1 to 627. 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
783406
2Even Fibonacci numbers
628257
3Largest prime factor
449521
4Largest palindrome product
399704
5Smallest multiple
407463
6Sum square difference
409842
710001st prime
350735
8Largest product in a series
295587
9Special Pythagorean triplet
298798
10Summation of primes
273931
11Largest product in a grid
198102
12Highly divisible triangular number
185462
13Large sum
191000
14Longest Collatz sequence
190728
15Lattice paths
157504
16Power digit sum
192767
17Number letter counts
128103
18Maximum path sum I
123043
19Counting Sundays
114332
20Factorial digit sum
168664
21Amicable numbers
123551
22Names scores
113972
23Non-abundant sums
87662
24Lexicographic permutations
97336
251000-digit Fibonacci number
131755
26Reciprocal cycles
70637
27Quadratic primes
73785
28Number spiral diagonals
92592
29Distinct powers
88763
30Digit fifth powers
92963
31Coin sums
71175
32Pandigital products
59924
33Digit cancelling fractions
60643
34Digit factorials
79788
35Circular primes
71998
36Double-base palindromes
75805
37Truncatable primes
62315
38Pandigital multiples
53081
39Integer right triangles
61775
40Champernowne's constant
67980
41Pandigital prime
57489
42Coded triangle numbers
63414
43Sub-string divisibility
50213
44Pentagon numbers
48754
45Triangular, pentagonal, and hexagonal
60411
46Goldbach's other conjecture
51590
47Distinct primes factors
48707
48Self powers
96674
49Prime permutations
48715
50Consecutive prime sum
52437