# Prime Numbers Calculator

## Check if a number is prime

Enter a **positive** integer to determine whether it is prime or not.

**Is prime?**

## Find the prime factors of a number

Enter a **positive **integer greater than 1 to separate it into its prime factors.

**Prime factors:**

The first prime number calculator allows you to determine if a number is prime or not. Additionally, with the second calculator, you can get the prime factors of any positive integer.

## How to use the prime number calculators?

**Step 1:** Determine which of the two calculators to use. If you want to know if a number is prime or not, use the first one. If you want to separate a number into its prime factors, use the second calculator.

**Step 2:** Enter the number into the first or second calculator. You must enter only positive whole numbers for the calculators to work correctly.

**Step 3:** The answer will be displayed in the corresponding box on the right.

## What are prime numbers?

Prime numbers are those numbers that are only divisible by 1 and by themselves. For example, the number 3 is prime since it can only be divided by 3 and 1. Note that 1 is not considered a prime number.

## Why is 1 not considered a prime number?

For a number to be prime, it must be divisible by two numbers, 1 and itself. In the case of 1, 1 and itself are the same number. That is, it has no other divisor. Therefore, 1 is not considered a prime number.

If we wanted 1 to be considered a prime number, we would have to change the definition of prime numbers.

## Are negative numbers considered prime numbers?

Negative numbers are not considered prime numbers, only positive numbers are considered prime numbers.

## How to determine if a number is prime?

One way to determine if a number is prime or not is to divide it by the small prime numbers until you determine if there is another number besides 1 and itself that divides it exactly.

For example, to determine whether 25 is prime, we can start by dividing it by 2, then 3, then 5, and so on until we find a number that divides it exactly. In this case, 5 divides it exactly, so 25 is not a prime number.

## Table of prime numbers up to 100

You can use the following table to have a reference of the prime numbers up to 100. The prime numbers are marked with the red circle.

## Related calculators:

- Least Common Multiple Calculator (MCM)
- Greatest Common Divisor Calculator (GCD)
- Binary Numbers Calculator

You can explore more calculators here.