# Is 638 A Prime Number

A prime number is a whole number with exactly two integral divisors, 1 and itself.

Let's check 638 number is prime.

## Check 638 Prime Number Or Not

Factors of 638 :- 1
- 2
- 11
- 22
- 29
- 58
- 319
- 638

The factors number for **638** is **8** so it is greater than 2 , that's why it can not be prime number.

## What Is Prime Number ?

Prime numbers are positive integers which have no divisors other than 1 and themselves so prime numbers can't be divided by other numbers than itself or 1. For example 2, 3, 5, 7, 11, 13, 17, 19, 23.... are the prime numbers.

## How to check if a number is prime ?

The method we use is to try to divide it by all numbers from 1 to itself.

**For example:**

Let's check 42 prime or not ?

For number 42 we have to divide from 1 to 42 to find the remainder is equal to 0.

Divisors are : 1 , 2 , 3 , 6 , 7 , 14 and 21. So there more than 2 divisors.

**The Answer** : 42 is not a prime number.

**Another example:**

Let's check 17 prime or not ?

For number 17 we have to divide from 1 to 17 to find the remainder is equal to 0.

1 and 17 are the only divisors for 17. There are 2 divisors.

**The Answer** : 17 is a prime number.