Question

What is a co-prime number?

Answer 1

Numbers, which do not have any common factor between them other than one, are called co-prime numbers.

Explanation:

When two numbers (they may not be prime) do not have any common factor other than one between them they are called co-prime or relatively prime.

It is obvious that two prime numbers are always co-prime. For example, `17` and `23`.

However, even two composite numbers can also be co-prime or relatively prime. For example `16` and `25` do not have any common factor other than one. Similarly `84` and `65` do not have any common factor and are hence co-prime.