Co-prime numbers

Set of  numbers that have only common divisor as 1 are called co-prime numbers.

Co-prime numbers are also known as Mutually prime number or Relatively prime numbers.

How to Check weather two numbers are Prime or not?

Consider any two numbers, if no positive integer divide both the numbers except 1 then the two numbers are called Relatively Prime or Co-prime.

Example1: are 15 and 22 co-prime?

Answer: 

Divisors of 15: 1, 3, 5, 15

Divisors of 22: 1,2,11,22

Since 15 and 22 don't have any common divisor they are co-prime.

Example2: are 20 and 34 co-prime?

Answer: 

Divisors of 20 : 1,2,4,5,10,20

Divisors of 34 : 1,2,17,34

These two numbers have 2 as the common divisors so they are not co-prime.

FACTS:

• Every number is co-prime with 1.
• Two even number can never be co-prime because every even number is divisible by 2.
• Every Prime number is co-prime to each other. 
• Any two consecutive number are always co-prime. Take any two number like (1,2), (2,3), (3,4)... (501,502).... are always co-prime.

                                                            

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