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Problems Archives

The problems archives table shows problems 1 to 548. 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
560054
2Even Fibonacci numbers
456220
3Largest prime factor
329749
4Largest palindrome product
296336
5Smallest multiple
307676
6Sum square difference
309413
710001st prime
265242
8Largest product in a series
227664
9Special Pythagorean triplet
228121
10Summation of primes
209666
11Largest product in a grid
154149
12Highly divisible triangular number
142189
13Large sum
148398
14Longest Collatz sequence
146806
15Lattice paths
121990
16Power digit sum
150356
17Number letter counts
100040
18Maximum path sum I
96924
19Counting Sundays
89715
20Factorial digit sum
134051
21Amicable numbers
96505
22Names scores
89451
23Non-abundant sums
68251
24Lexicographic permutations
76864
251000-digit Fibonacci number
103908
26Reciprocal cycles
55407
27Quadratic primes
58112
28Number spiral diagonals
74446
29Distinct powers
69640
30Digit fifth powers
73376
31Coin sums
55484
32Pandigital products
47222
33Digit cancelling fractions
48083
34Digit factorials
63444
35Circular primes
57592
36Double-base palindromes
60840
37Truncatable primes
49426
38Pandigital multiples
42027
39Integer right triangles
48760
40Champernowne's constant
54038
41Pandigital prime
45450
42Coded triangle numbers
50917
43Sub-string divisibility
39268
44Pentagon numbers
38046
45Triangular, pentagonal, and hexagonal
48347
46Goldbach's other conjecture
40338
47Distinct primes factors
38335
48Self powers
78701
49Prime permutations
38256
50Consecutive prime sum
41069