Prime Number Checker
Check if any positive integer is a prime number. A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself. For composite numbers, this tool also shows all factors. Essential for cryptography and number theory.
Check if Number is Prime
Test Numbers
Numbers highlighted are prime
First 25 Prime Numbers
FAQ
What is a prime number?
A prime number is a natural number greater than 1 that cannot be formed by multiplying two smaller natural numbers. The first primes are 2, 3, 5, 7, 11, 13, 17, 19, 23, 29.
Why is 1 not considered prime?
By mathematical convention, 1 is not prime because the fundamental theorem of arithmetic requires unique prime factorization, which would fail if 1 were prime (e.g., 6 = 2 x 3 = 1 x 2 x 3).
Why are prime numbers important?
Primes are the building blocks of all integers. They are crucial in cryptography (RSA encryption relies on the difficulty of factoring large numbers), hash functions, and random number generation.