Prime Number Checker & Factorizer
Check if any number is prime and find its complete prime factorization. Tests numbers instantly with factor breakdown.
Runs in your browser. No data leaves your device.
Frequently Asked Questions
How does the Prime Number Checker work?
The tool uses trial division: it tests whether the input is divisible by any integer from 2 up to the square root of the number. If no divisor is found, the number is prime. For factorization, it repeatedly divides by the smallest prime factor and collects the results until the quotient is 1.
What is a prime number?
A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself. Examples include 2, 3, 5, 7, 11, 13, 17, and 19.
How large of a number can I check?
The tool handles numbers up to JavaScript's safe integer limit (about 9 quadrillion). Primality testing is instant for most numbers you would encounter in schoolwork or programming.
What is prime factorization?
Prime factorization breaks a number into the product of prime numbers. For example, 60 = 2 x 2 x 3 x 5. Every whole number greater than 1 has a unique prime factorization.