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Problems Archives

The problems archives table shows problems 1 to 646. 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
825853
2Even Fibonacci numbers
660455
3Largest prime factor
471897
4Largest palindrome product
418338
5Smallest multiple
425391
6Sum square difference
428012
710001st prime
365899
8Largest product in a series
307270
9Special Pythagorean triplet
311324
10Summation of primes
285036
11Largest product in a grid
205527
12Highly divisible triangular number
192627
13Large sum
198090
14Longest Collatz sequence
197930
15Lattice paths
163474
16Power digit sum
200038
17Number letter counts
132566
18Maximum path sum I
127152
19Counting Sundays
118347
20Factorial digit sum
174402
21Amicable numbers
127863
22Names scores
117800
23Non-abundant sums
90706
24Lexicographic permutations
100638
251000-digit Fibonacci number
136415
26Reciprocal cycles
73151
27Quadratic primes
76252
28Number spiral diagonals
95663
29Distinct powers
91795
30Digit fifth powers
96160
31Coin sums
73837
32Pandigital products
61923
33Digit cancelling fractions
62572
34Digit factorials
82501
35Circular primes
74221
36Double-base palindromes
78176
37Truncatable primes
64238
38Pandigital multiples
54777
39Integer right triangles
63762
40Champernowne's constant
70136
41Pandigital prime
59358
42Coded triangle numbers
65291
43Sub-string divisibility
51838
44Pentagon numbers
50448
45Triangular, pentagonal, and hexagonal
62311
46Goldbach's other conjecture
53282
47Distinct primes factors
50267
48Self powers
99593
49Prime permutations
50290
50Consecutive prime sum
54165