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The problems archives table shows problems 1 to 997. If you would like to tackle the 10 most recently published problems, go to Recent problems.



ID

 Title
Solved By
1Multiples of 3 or 5
859961
2Even Fibonacci Numbers
687322
3Largest Prime Factor
517361
4Largest Palindrome Product
457156
5Smallest Multiple
443577
6Sum Square Difference
448504
710 001st Prime
390810
8Largest Product in a Series
332430
9Special Pythagorean Triplet
338138
10Summation of Primes
317314
11Largest Product in a Grid
237374
12Highly Divisible Triangular Number
233663
13Large Sum
234383
14Longest Collatz Sequence
238759
15Lattice Paths
202450
16Power Digit Sum
236996
17Number Letter Counts
169716
18Maximum Path Sum I
163980
19Counting Sundays
153789
20Factorial Digit Sum
207015
21Amicable Numbers
169090
22Names Scores
155803
23Non-Abundant Sums
128343
24Lexicographic Permutations
137539
25$1000$-digit Fibonacci Number
175363
26Reciprocal Cycles
104501
27Quadratic Primes
108003
28Number Spiral Diagonals
126723
29Distinct Powers
127743
30Digit Fifth Powers
132490
31Coin Sums
104311
32Pandigital Products
88880
33Digit Cancelling Fractions
88698
34Digit Factorials
114856
35Circular Primes
102921
36Double-base Palindromes
107421
37Truncatable Primes
90852
38Pandigital Multiples
78074
39Integer Right Triangles
89783
40Champernowne's Constant
96866
41Pandigital Prime
84226
42Coded Triangle Numbers
89776
43Sub-string Divisibility
74192
44Pentagon Numbers
72773
45Triangular, Pentagonal, and Hexagonal
86218
46Goldbach's Other Conjecture
76327
47Distinct Primes Factors
71807
48Self Powers
122982
49Prime Permutations
71410
50Consecutive Prime Sum
76521