Check whether a number is prime and see its factors.
Calculated locally in your browser.
Understanding your result
1 is not prime, and the only even prime is 2.
Formula and method
A prime number greater than 1 has exactly two factors: 1 and itself. The tool tests divisibility up to the square root.
Worked example
17 is prime; 18 is not (its factors are 1, 2, 3, 6, 9, 18).
How to use this tool
- Enter a whole number.
- See whether it is prime and its factors.
Common mistakes to avoid
- Assuming 1 is prime — it is not.
About the Prime Number Checker
Check whether a whole number is prime, list its factors and find the next prime.
Frequently asked questions
Is 2 prime?
Yes. 2 is the smallest and only even prime number.