HCF of Co-prime Number is Always

Answer: 

Two integer numbers

x and y, are said to be coprime if they have only 1 as their common factor.

Therefore, the HCF of two coprime numbers is always 1. 

If you need to find whether any two numbers are co-prime or not, first find their Greatest Common Factor (GCF). If  GCF comes 1, then we can say that they are co-prime.

For example, if we take:

1. 4 and 7

2. 5, 7 and 9 are co-prime numbers. 

Co-prime numbers do not always need to be prime numbers. 

Two composite numbers like 4 and 9 also form a pair of co-primes.