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Problems Archives

The problems archives table shows problems 1 to 641. 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
815810
2Even Fibonacci numbers
652788
3Largest prime factor
466603
4Largest palindrome product
413855
5Smallest multiple
421204
6Sum square difference
423763
710001st prime
362376
8Largest product in a series
304615
9Special Pythagorean triplet
308480
10Summation of primes
282444
11Largest product in a grid
203840
12Highly divisible triangular number
191045
13Large sum
196440
14Longest Collatz sequence
196287
15Lattice paths
162155
16Power digit sum
198351
17Number letter counts
131519
18Maximum path sum I
126220
19Counting Sundays
117437
20Factorial digit sum
173066
21Amicable numbers
126874
22Names scores
116928
23Non-abundant sums
90010
24Lexicographic permutations
99910
251000-digit Fibonacci number
135356
26Reciprocal cycles
72587
27Quadratic primes
75685
28Number spiral diagonals
95017
29Distinct powers
91095
30Digit fifth powers
95457
31Coin sums
73323
32Pandigital products
61482
33Digit cancelling fractions
62146
34Digit factorials
81904
35Circular primes
73736
36Double-base palindromes
77645
37Truncatable primes
63804
38Pandigital multiples
54394
39Integer right triangles
63333
40Champernowne's constant
69622
41Pandigital prime
58961
42Coded triangle numbers
64876
43Sub-string divisibility
51466
44Pentagon numbers
50039
45Triangular, pentagonal, and hexagonal
61864
46Goldbach's other conjecture
52887
47Distinct primes factors
49906
48Self powers
98971
49Prime permutations
49948
50Consecutive prime sum
53805