# Prime Numbers Calculator

Using the prime number calculator below, you can perform a primality test for any number. This means that you can enter any number and check if it is a prime number or not. This prime number checker is a free online tool for students and mathematicians. This tool can also be used to find all the factors of a number.
Prime numbers are positive numbers that have two factors. The numbers with one factor or more than two factors are not classified as prime numbers. They have a maximum of 13 digits that is, less than 10 trillion.

## How to use the prime number checker tool

Step 1: Click on the textbox to enter the number that you need to check. A number pad will slide up that you can use to key in your number.
Step 2: Click on the Check button to find whether the number is prime or not.
Step 3: The results are shown along with the reason why the number is or isn’t a prime number.
To clear the entered number, click on the Reset button.

## Examples to check on prime number tool

Before you use the tool, have a look at these examples and use them on the prime number calculator:

Is 5 a prime number?
Yes, 5 is a prime number as it has exactly two factors, 1 and 5.

Is 19 a prime number?
Yes, 19 is a prime number as it has two factors, 1 and 19.

Is 91 a prime number?
No, 91 is NOT a prime number because it has more than two factors. 91 is a composite number and can be factored by any of the following numbers: 1, 7, 13, 91.

Online Math Classes > Math Calculators > Prime numbers calculator

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