Number System

1. Perfect Numbers:
   
     A number, the sum of whose factors is equal to the number is called Perfect number.
Eg:
        6, 28, 496

2. Co-Prime (or) Relational Primes:

     Two number whose HCF is 1 are called Co-Prime number.
Eg:
       (2, 3), (8, 9)

3. Twin Prime:
   
       Number which can be expressed in the form p/q, where p and q are integers and q(not equal to zero) called Rational number.
Eg:
       1/8, -8/11, 0, 6, 5 2/3

4. Irrational Number:

       Number which when expressed in decimal would be in non-terminating and non-repeating form, are called irrational number.
Eg: