How to use this calculator
Check whether a positive integer is prime using deterministic trial division for practical browser-sized values.
How the calculation works
- Enter an integer.
- The calculator checks divisibility up to the square root.
- If composite, one factor is shown.
Formula
A number n is prime if it has no divisors greater than 1 and less than or equal to sqrt(n).
Example
97 is prime; 91 is not prime because it is divisible by 7.
Understanding your result
Use the output as a practical starting point, then review it before using it in an important workflow.
Assumptions and limitations
- Very large primality testing is intentionally out of scope for V1.
- Numbers 1 and below are not prime.
Frequently asked questions
Does this require an account?
No. The core tool works without creating a Tool2Do account.
Is my input included in share links or analytics?
No. Tool2Do share actions use the tool page URL and safe metadata, not private values or uploaded files.