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Problems Archives

The problems archives table shows problems 1 to 609. 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
726510
2Even Fibonacci numbers
584909
3Largest prime factor
419184
4Largest palindrome product
373680
5Smallest multiple
382533
6Sum square difference
384750
710001st prime
329366
8Largest product in a series
278809
9Special Pythagorean triplet
281361
10Summation of primes
258188
11Largest product in a grid
187638
12Highly divisible triangular number
175033
13Large sum
180765
14Longest Collatz sequence
180167
15Lattice paths
149017
16Power digit sum
182456
17Number letter counts
121479
18Maximum path sum I
116760
19Counting Sundays
108515
20Factorial digit sum
160263
21Amicable numbers
116932
22Names scores
108080
23Non-abundant sums
83035
24Lexicographic permutations
92373
251000-digit Fibonacci number
125004
26Reciprocal cycles
67054
27Quadratic primes
70134
28Number spiral diagonals
88419
29Distinct powers
84233
30Digit fifth powers
88259
31Coin sums
67431
32Pandigital products
56953
33Digit cancelling fractions
57654
34Digit factorials
75941
35Circular primes
68547
36Double-base palindromes
72168
37Truncatable primes
59208
38Pandigital multiples
50465
39Integer right triangles
58639
40Champernowne's constant
64686
41Pandigital prime
54603
42Coded triangle numbers
60454
43Sub-string divisibility
47564
44Pentagon numbers
46194
45Triangular, pentagonal, and hexagonal
57481
46Goldbach's other conjecture
48902
47Distinct primes factors
46256
48Self powers
92255
49Prime permutations
46234
50Consecutive prime sum
49752