Check if any number is prime and find prime factors instantly.
The Prime Number Checker instantly determines if a number is prime or composite and provides its full list of factors.
n is prime if it has exactly 2 factors.Prime numbers are the "atoms" of mathematics. A prime number is a whole number greater than 1 that cannot be formed by multiplying two smaller whole numbers. Numbers that are not prime are called composite numbers.
This theorem states that every integer greater than 1 either is prime itself or is the product of prime numbers, and that this product is unique. For example, 12 = 2 × 2 × 3.
Prime numbers are essential for modern digital security. The RSA encryption algorithm, which secures your credit card transactions and private messages, relies on the fact that it is very easy to multiply two large prime numbers but extremely difficult for a computer to factor the result back into the original primes.
To check if a number (n) is prime, we only need to test divisibility by integers up to the square root of n (√n). If no factor is found by that point, the number is guaranteed to be prime.
17 is prime. 15 is composite (3 × 5). 1 is neither prime nor composite.