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## Problems Archives

The problems archives table shows problems 1 to 662. 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
851849
2Even Fibonacci numbers
680537
3Largest prime factor
486201
4Largest palindrome product
430803
5Smallest multiple
437010
6Sum square difference
439795
710001st prime
375918
8Largest product in a series
314971
9Special Pythagorean triplet
319548
10Summation of primes
292563
11Largest product in a grid
210364
12Highly divisible triangular number
197335
13Large sum
202814
14Longest Collatz sequence
202648
15Lattice paths
167276
16Power digit sum
204841
17Number letter counts
135499
18Maximum path sum I
129987
19Counting Sundays
120821
20Factorial digit sum
178322
21Amicable numbers
130729
22Names scores
120334
23Non-abundant sums
92655
24Lexicographic permutations
102679
251000-digit Fibonacci number
139415
26Reciprocal cycles
74701
27Quadratic primes
77811
28Number spiral diagonals
97462
29Distinct powers
93807
30Digit fifth powers
98256
31Coin sums
75438
32Pandigital products
63199
33Digit cancelling fractions
63831
34Digit factorials
84196
35Circular primes
75705
36Double-base palindromes
79713
37Truncatable primes
65531
38Pandigital multiples
55887
39Integer right triangles
65061
40Champernowne's constant
71532
41Pandigital prime
60545
42Coded triangle numbers
66601
43Sub-string divisibility
52891
44Pentagon numbers
51522
45Triangular, pentagonal, and hexagonal
63520
46Goldbach's other conjecture
54428
47Distinct primes factors
51334
48Self powers
101562
49Prime permutations
51310
50Consecutive prime sum
55323