Types of Numbers

• Natural Numbers:

       Natural numbers are counting numbers. They are denoted by ‘N’.

                 N = {1, 2, 3, …} 

• Whole Numbers:

      All natural numbers and zero form the set of whole numbers. Whole numbers are denoted by ‘W’.

      W = {0, 1, 2, 3, …}

• Integers:

      Whole numbers and negative numbers form the set of integers. They are denoted by ‘I’.

       I = {…, -4, -3, -2, -1, 0, 1, 2, 3, 4, …}

• Even Numbers:

      A counting number which is divisible by 2, is called an even number.

     0, 2, 4, 6, 8, 10, … etc.

• Odd Numbers:

      A counting number which is not divisible by 2, is known as ODD number.

      1, 3, 5, 7, … etc.

• Prime Numbers:

      A counting number is called a prime number when it is exactly divisible by 1 and itself.

      2, 3, 5, 7, 11, 13, … etc.

• Composite Numbers:

      Composite numbers are non-prime natural numbers. They must have at least one factor apart from  and itself.

       4, 6, 8, 9 etc.

• Coprimes:

      Two natural numbers are said to be Coprimes, if their HCF is 1.

      (7, 9), (15, 16)

• Rational Numbers:

      A number that can be expressed as p/q is called a rational number, p and q are integers and p ≠ 0.

      3/5, 7/9, 8/9 etc.

• Irrational Numbers:

      The numbers that cannot be expressed in the form of p/q are called irrational

and q are integers and p ≠ 0.

      √2, √3, √7 etc.

• Real Numbers:

      Real Numbers include rational and irrational numbers both.

      7/9, √2, √5, ∏, 8/9 etc.