Prime Number Checker
Test any whole number for primality and, if it is composite, see its prime factors.
How to use it
- Enter a whole number Any non-negative integer works.
- Read the result You'll see whether it is prime, and its prime factors if it isn't.
Examples
| 97 | prime |
|---|---|
| 360 | 2³ × 3² × 5 |
| 1 | not prime |
About this tool
A prime number has exactly two divisors: 1 and itself. Primes are the building blocks of arithmetic — every whole number above 1 is either prime or a unique product of primes.
This tool checks primality using efficient trial division and, for composite numbers, shows the full prime factorization. It works entirely in your browser.
Frequently asked questions
What is a prime number?
A prime is a whole number greater than 1 whose only divisors are 1 and itself. The first few are 2, 3, 5, 7 and 11.
Is 1 a prime number?
No. By definition a prime must be greater than 1, so 1 is neither prime nor composite.
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Updated June 12, 2026