Prime Number Checker
Enter a whole number to instantly check whether it is a prime number, and see nearby primes.
What this calculator does
This tool checks whether a whole number is a prime number — a number greater than 1 that has no divisors other than 1 and itself. It also shows the nearest prime numbers before and after your entry, and the smallest factor if the number is not prime.
How the check works
The calculator uses trial division: it tests whether any whole number from 2 up to the square root of your number divides evenly into it. If none do, the number is prime. This is a standard and efficient method for checking primality of numbers within a normal calculator range.
Good to know
By definition, 0 and 1 are not prime, and all even numbers except 2 are not prime. This tool is intended for general educational and reference use.