Explore number sets
Browse numbers by mathematical property: primes, Fibonacci, perfect squares, palindromes, and more.
Prime numbers
An integer greater than 1 divisible only by 1 and itself.
Examples: 2, 3, 5
Fibonacci numbers
Each term equals the sum of the two previous terms in 0, 1, 1, 2, 3, 5…
Examples: 0, 1, 1
Perfect squares
A number equal to n² for some integer n.
Examples: 0, 1, 4
Perfect cubes
A number equal to n³ for some integer n.
Examples: 0, 1, 8
Triangular numbers
A number equal to the sum 1+2+…+n.
Examples: 0, 1, 3
Perfect numbers
A number equal to the sum of its proper divisors.
Examples: 6, 28, 496
Palindrome numbers
A number that reads the same forward and backward in decimal.
Examples: 0, 1, 121
Powers of two
A number equal to 2^k for integer k.
Examples: 1, 2, 4
Even numbers
An integer divisible by 2.
Examples: 0, 2, 4
Odd numbers
An integer not divisible by 2.
Examples: 1, 3, 5