Prime Numbers Definition

The prime number is the one that has only two factors i.e. 1 and the number itself. In simple words, we can say a number that can’t be divided by any other number completely is said to be Prime Number. It can have a maximum of two factors on this page.


You can read about Factors here.

Table of Contents

It is also considered the opposite of Composite numbers (Numbers with at least three factors). For example, 7 is the prime number because it can’t be divided by any other number with 0 remainders left.


Read about Composite Numbers here.

Prime Numbers less than 30.

3, 5, 7, 11, 13, 17, 19, 23, 29.

Terms related to Prime Numbers

There are two main terms related to Prime Numbers that we are going to mention here.

  • Co-Prime: Two numbers that have only one common factor i.e. “1”. For example, 9 and 10 are prime numbers because they have 1 as their common factor only.
  • Twin Prime: The pair of prime numbers is called a Twin Prime if it has only one composite number between them. For example, (3, 5), (11, 13), and (5, 7) are Twin Primes because they have only one composite number between them.

How to check if a number is prime or not?

You can easily find if the given number is prime or not just by dividing it by different terms. If a number is divisible by any other number except 1 and by the number itself, it is not called a Prime Number.

Example 1:

Check whether 16 is a prime number or not.


Let us divide 16 with different prime numbers less than 16.

  • 16 is divisible by 2, 4, and 8.

It shows that 16 is not a Prime number because it has 3 more factors except 1..

Example 1:

Check whether 31 is a Prime number.


By using our division testing, we have found that 31 is not divisible by any whole number. That is why 31 is termed to be a Prime Number.

Fun Facts of Sum

  • 2 is the smallest prime number.
  • The only even number that is prime too is “2”.
  • 2 & 3 are only consecutive prime numbers.
  • 0 & 1 is neither a prime nor a composite number.
  • All numbers ending with 5 except 5 can’t be prime numbers.
  • The occurrence of prime numbers reduces with the increase in value.


Is 1 a Prime number?

No, 1 is neither a prime number nor a composite number. It is part of the Natural and Whole number set only.

What is the smallest prime number?

“2” is the smallest prime number.

Are all odd numbers prime?

No, odd numbers can be prime or composite. But all even numbers except 2 are composite numbers.

Can a prime number be negative?

No, a prime number can’t be negative. It is called an Integer only instead of giving any other name.

What is the difference between prime numbers and composite numbers?

Prime numbers have only two factors including 1 while Composite numbers have at least three factors including 1.