## Number System

##### Natural numbers {N}

The counting numbers {1, 2, 3, 4, 5…} are called natural numbers;

##### Whole numbers

Natural numbers including 0 {0, 1, 2, 3, 4, 5…} are also called **whole numbers**.

Negative numbers are not considered “whole numbers.”

##### Integers {Z}

Positive and negative counting numbers, as well as zero: {…, −3, −2, −1, 0, 1, 2, 3, …} are called integers.

##### Even Number

The Numbers divisible by 2 are known as Even Numbers.

Even Numbers – 2,4,6,8,10,12,14,16,18 and so on.

##### Odd Numbers

The Numbers which are not divisible by 2 are known as Odd Numbers. In other words, the odd numbers are those numbers that are not even.

Odd Numbers – 1, 3, 5, 7, 9, 11, 13, 15, 17, and so on.

##### Prime Number

The numbers are divisible by one and itself and not divisible by any other number.

Prime Numbers are: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29 and so on.

##### Rational Number

Any number which can be expressed in the form of, where a and b both are integers and, b 0 is a rational number.

Example – 5/6, 2/3, 5/4.

##### Composite Numbers

A composite number is a whole number (greater than 1) that is not prime.

Composite numbers C= (4,6,8,9 ……..,etc.)