 # Number System

## 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 that are 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 which are not even.

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

### Prime Number

The numbers that 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 is not equal to 0 is a rational number. Ex – 3/5, 2/6. 9/8.

### Composite Numbers

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

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

### Number System

• Every number, which is either rational or irrational is called a real number.
• Each natural number is a real number.
• Each whole number is a real number.
• Each integer is a real number.
• Each rational number is a real number.
• Each irrational number is a real number, etc.

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