## What is Prime Number?

Any Natural number greater than **1**, which is divisible by **1** and only by itself is called Prime
Number.

**2, 3, 5, 7, 11** etc.

**2** is the smallest Prime Number.

## Arrangement of prime numbers

Prime numbers can be arranged in a line form like shown as below in the diagram.

## What is composite number?

Any Natural number, which is greater than **1** and is not a Prime Number is called a Composite Number.

**4, 6, 8, 9, 10**
etc.

**1** is neither a Prime Number nor Composite Number.

Every number in maths can either be a prime or a composite number except 0 and 1 because 0 and 1 are neither a prime number nor a composite number.

## Arrangement of composite numbers

Composite numbers can be arranged in a rectangular or square form like shown as below in the diagram.

## What are coprimes?

Two numbers are called to be coprime or co-prime if they have only **1** as a common factor.

In other way, we can say if greatest common divisor of two numbers is 1, then the two numbers are coprimes.

**(2,3), (14,15), (8,13)** etc.

## What is twin prime?

Two numbers are called Twin Prime if they differ by 2 only or we can say that there is only one composite number between them. One prime number can be 2 more or 2 less than another prime number.

**(3,5), (29,31), (71,73)** etc.

## What are prime triplets?

A set of three consecutive Prime Numbers if the smallest and the largest differ by 6 and must be in the form of (p, p + 2, p + 6) is called a Prime Triplet.

**(5,7,11)**

Why?

Because, 5, 7 and 11 is in the form of p, p + 2, p + 6

where p = 5

p + 2 = 5 + 2 = 7

and p + 6 = 5 + 6 = 11