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Problem Archives

The problems archives table shows problems 1 to 1007. 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
848178
2Even Fibonacci Numbers
678658
3Largest Prime Factor
512179
4Largest Palindrome Product
452909
5Smallest Multiple
439388
6Sum Square Difference
444448
710 001st Prime
387361
8Largest Product in a Series
330287
9Special Pythagorean Triplet
335723
10Summation of Primes
315237
11Largest Product in a Grid
236556
12Highly Divisible Triangular Number
232897
13Large Sum
233681
14Longest Collatz Sequence
238063
15Lattice Paths
202127
16Power Digit Sum
236422
17Number Letter Counts
169694
18Maximum Path Sum I
164098
19Counting Sundays
153898
20Factorial Digit Sum
207010
21Amicable Numbers
169219
22Names Scores
155906
23Non-Abundant Sums
128775
24Lexicographic Permutations
137876
25$1000$-digit Fibonacci Number
175374
26Reciprocal Cycles
104901
27Quadratic Primes
108394
28Number Spiral Diagonals
127125
29Distinct Powers
128052
30Digit Fifth Powers
132930
31Coin Sums
104613
32Pandigital Products
89221
33Digit Cancelling Fractions
89119
34Digit Factorials
115277
35Circular Primes
103226
36Double-base Palindromes
107867
37Truncatable Primes
91198
38Pandigital Multiples
78362
39Integer Right Triangles
90155
40Champernowne's Constant
97138
41Pandigital Prime
84482
42Coded Triangle Numbers
90183
43Sub-string Divisibility
74529
44Pentagon Numbers
73050
45Triangular, Pentagonal, and Hexagonal
86578
46Goldbach's Other Conjecture
76611
47Distinct Primes Factors
72067
48Self Powers
123195
49Prime Permutations
71668
50Consecutive Prime Sum
76799