Prime Number Checker

Check instantly whether a number is prime or not.

Enter a whole number

Enter a positive whole number to check whether it is prime.

Result

What is a Prime Number?

A prime number is a whole number greater than 1 that has exactly two positive factors: 1 and itself.

Examples of prime numbers include 2, 3, 5, 7, 11, 13, 17, 19 and 23.

What is a Composite Number?

A composite number is a whole number greater than 1 that has more than two factors. For example, 12 has factors 1, 2, 3, 4, 6 and 12.

How to Use the Prime Number Checker

Enter a whole number and click "Check Number". The calculator will tell you whether the number is prime or not and will display its factors when applicable.

Related Math Calculators

Explore more free math tools from Easy Online Tool:

Prime Number Checker FAQs

What is a prime number?

A prime number is a whole number greater than 1 that has exactly two positive factors: 1 and the number itself.

Is 1 a prime number?

No. The number 1 is neither prime nor composite because it has only one positive factor.

Is 2 a prime number?

Yes. 2 is the smallest prime number and the only even prime number.

Is 0 a prime number?

No. Zero is neither prime nor composite.

How can I check if a large number is prime?

Enter the whole number into the calculator above. The tool checks whether the number has any divisor other than 1 and itself.