Prime Number Checker
Check whether an integer is prime and, if not, see a small factor explanation.
This tool checks whether n is a prime integer greater than 1.
Result will appear here.
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Privacy: calculations run locally in your browser. No values are stored or transmitted.
How it works
A number is prime if it has no positive divisors other than 1 and itself. This checker tests divisibility up to the square root of the input.
Examples
- 29 is prime
- 21 is not prime because 21 = 3 × 7
- 1 is not prime
FAQ
- What is a prime number?
A prime number is an integer greater than 1 that has exactly two positive divisors: 1 and itself.
- Are 0 and 1 prime?
No. Prime numbers must be greater than 1.
- Can negative numbers be prime?
No. In standard school and number theory usage, prime numbers are positive integers greater than 1.
- Are calculations stored?
No. Everything runs locally in your browser.