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Problems Archives

The problems archives table shows problems 1 to 713. 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.


ID

Description / TitleSolved By
1Multiples of 3 and 5
964021
2Even Fibonacci numbers
767014
3Largest prime factor
549412
4Largest palindrome product
485183
5Smallest multiple
488811
6Sum square difference
491840
710001st prime
420140
8Largest product in a series
350817
9Special Pythagorean triplet
356326
10Summation of primes
325980
11Largest product in a grid
232738
12Highly divisible triangular number
219490
13Large sum
224662
14Longest Collatz sequence
225011
15Lattice paths
185241
16Power digit sum
227373
17Number letter counts
149776
18Maximum path sum I
143266
19Counting Sundays
133147
20Factorial digit sum
196618
21Amicable numbers
144620
22Names scores
132582
23Non-abundant sums
102424
24Lexicographic permutations
113043
251000-digit Fibonacci number
153676
26Reciprocal cycles
82369
27Quadratic primes
85744
28Number spiral diagonals
106565
29Distinct powers
103791
30Digit fifth powers
108424
31Coin sums
83506
32Pandigital products
69760
33Digit cancelling fractions
70216
34Digit factorials
92726
35Circular primes
83118
36Double-base palindromes
87264
37Truncatable primes
72088
38Pandigital multiples
61574
39Integer right triangles
71665
40Champernowne's constant
78521
41Pandigital prime
66611
42Coded triangle numbers
72891
43Sub-string divisibility
58325
44Pentagon numbers
57013
45Triangular, pentagonal, and hexagonal
69548
46Goldbach's other conjecture
60089
47Distinct primes factors
56509
48Self powers
110633
49Prime permutations
56422
50Consecutive prime sum
61000