Prime Number Checker
Check if a number is prime and find primes in a range
Prime Number Checker is a free online tool from BrowserUtils that check if a number is prime and find primes in a range. It runs entirely in your browser — your data never leaves your device. No account required.
97 is PRIME
How to use Prime Number Checker
- 1Paste or type your input into the editor above.
- 2The tool processes your data instantly — right in your browser, with nothing sent to a server.
- 3Copy the result with one click or continue editing your input.
About Prime Number Checker
Free online prime number checker. Test if any number is prime and generate a list of all prime numbers within a given range. This tool runs entirely in your browser — your data is never sent to a server. Just paste your input, get instant results, and copy with one click. No sign-up or installation required.
Prime Number Checker specs
- Runtime
- 100% client-side (browser)
- Cost
- Free — no account, no rate limits, no usage caps
- Browser support
- Chrome 90+, Firefox 88+, Safari 14+, Edge 90+
- Last updated
- July 2, 2026
- Part of
- 299 developer tools on BrowserUtils (100% client-side)
Questions
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. The first few primes are 2, 3, 5, 7, 11, 13, 17, 19, 23, and 29.
Is 1 a prime number?
No. By definition, a prime number must be greater than 1. The number 1 is neither prime nor composite; it is a unit.
How does the prime number checker test if a number is prime?
The tool checks divisibility by all integers from 2 up to the square root of the input. If no divisor is found, the number is prime. This is efficient because any factor larger than the square root would pair with a smaller one already tested.
Can I generate a list of all primes in a range?
Yes. Enter a start and end value to generate every prime number within that range. This is useful for math homework, cryptography research, or exploring the distribution of primes.
Is 2 the only even prime number?
Yes. 2 is the only even prime because every other even number is divisible by 2. All primes greater than 2 are odd.
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