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## Problems Archives

The problems archives table shows problems 1 to 621. 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
767437
2Even Fibonacci numbers
616213
3Largest prime factor
441107
4Largest palindrome product
392459
5Smallest multiple
400496
6Sum square difference
402894
710001st prime
344814
8Largest product in a series
291019
9Special Pythagorean triplet
294081
10Summation of primes
269684
11Largest product in a grid
195315
12Highly divisible triangular number
182649
13Large sum
188269
14Longest Collatz sequence
187844
15Lattice paths
155247
16Power digit sum
189946
17Number letter counts
126293
18Maximum path sum I
121351
19Counting Sundays
112789
20Factorial digit sum
166379
21Amicable numbers
121801
22Names scores
112443
23Non-abundant sums
86421
24Lexicographic permutations
96019
251000-digit Fibonacci number
129955
26Reciprocal cycles
69674
72805
28Number spiral diagonals
91476
29Distinct powers
87544
30Digit fifth powers
91744
31Coin sums
70191
32Pandigital products
59142
33Digit cancelling fractions
59857
34Digit factorials
78783
35Circular primes
71037
36Double-base palindromes
74885
37Truncatable primes
61480
38Pandigital multiples
52365
39Integer right triangles
60948
40Champernowne's constant
67115
41Pandigital prime
56728
42Coded triangle numbers
62639
43Sub-string divisibility
49494
44Pentagon numbers
48092
45Triangular, pentagonal, and hexagonal
59608
46Goldbach's other conjecture
50869
47Distinct primes factors
48050
48Self powers
95495
49Prime permutations
48046
50Consecutive prime sum
51738