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Problems Archives

The problems archives table shows problems 1 to 689. 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
914744
2Even Fibonacci numbers
728686
3Largest prime factor
520780
4Largest palindrome product
460297
5Smallest multiple
465332
6Sum square difference
468406
710001st prime
399935
8Largest product in a series
334244
9Special Pythagorean triplet
339401
10Summation of primes
310490
11Largest product in a grid
222166
12Highly divisible triangular number
208919
13Large sum
214446
14Longest Collatz sequence
214616
15Lattice paths
176770
16Power digit sum
216860
17Number letter counts
142982
18Maximum path sum I
136933
19Counting Sundays
127365
20Factorial digit sum
188065
21Amicable numbers
138042
22Names scores
126746
23Non-abundant sums
97739
24Lexicographic permutations
108107
251000-digit Fibonacci number
147093
26Reciprocal cycles
78704
27Quadratic primes
81960
28Number spiral diagonals
102353
29Distinct powers
99179
30Digit fifth powers
103763
31Coin sums
79718
32Pandigital products
66603
33Digit cancelling fractions
67177
34Digit factorials
88750
35Circular primes
79652
36Double-base palindromes
83700
37Truncatable primes
68991
38Pandigital multiples
58895
39Integer right triangles
68539
40Champernowne's constant
75271
41Pandigital prime
63675
42Coded triangle numbers
69884
43Sub-string divisibility
55700
44Pentagon numbers
54435
45Triangular, pentagonal, and hexagonal
66726
46Goldbach's other conjecture
57427
47Distinct primes factors
54096
48Self powers
106525
49Prime permutations
53990
50Consecutive prime sum
58319