Using the prime number checker 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 calculator 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 check prime number online

Step 1: Click on the textbox to enter the number that you need to check. A numberpad 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 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

### 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.

A Prime number checker is a tool or program used to determine whether a given number is a prime number or not. Prime numbers are a fundamental concept in mathematics and play a crucial role in various mathematical and scientific fields, such as cryptography, coding theory, and number theory.

A prime number is a positive integer greater than 1 that is only divisible by 1 and itself. For example, the first six prime numbers are 2, 3, 5, 7, 11, and 13. Prime numbers have several properties that make them important in mathematical and scientific applications, such as the fact that they cannot be expressed as the product of two smaller numbers.

There are various methods for checking whether a number is prime or not, including trial division, the sieve of Eratosthenes, and the Miller-Rabin primality test. The trial division method involves dividing the number to be checked by every integer greater than 1 and less than the square root of the number. If the number is only divisible by 1 and itself, then it is prime. The sieve of Eratosthenes is an algorithm that generates a list of prime numbers up to a given limit by marking multiples of prime numbers as composite and then identifying the remaining unmarked numbers as prime. The Miller-Rabin primality test is a probabilistic algorithm that checks whether a number is prime by performing a series of modular exponentiations.

Prime number checkers can also be used in various mathematical and scientific applications, such as solving Diophantine equations, finding solutions to mathematical problems, and developing algorithms for various mathematical operations.

A Prime number checker is a tool or program used to determine whether a given number is a prime number or not. Prime numbers are important in various mathematical and scientific fields and have several properties that make them useful in mathematical and scientific applications. Prime number checkers can be implemented in various programming languages and can be used for a variety of purposes, such as finding prime numbers, generating lists of prime numbers, and finding the largest prime factor of a given number. They can also be used in mathematical and scientific applications, such as solving Diophantine equations and developing algorithms for mathematical operations.