Are 28 and 45 relatively prime?

In mathematics, two integers a and b are said to be relatively prime, if the only positive integer that evenly divides both of them is 1. For example, 28 and 45 are relatively prime because the only positive integer that divides both of them is 1. The concept of relatively prime is important in number theory, because many theorems and results are stated in terms of relatively prime integers. For example, the Chinese Remainder Theorem is a statement about relatively prime integers. Relatively prime numbers also have applications in cryptography. For example, the RSA algorithm for public-key encryption uses two large prime numbers that are relatively prime. In general, if a and b are relatively prime, then the number of positive integers less than or equal to a that are relatively prime to a is equal to the number of positive integers less than or equal to b that are relatively prime to b. This is a consequence of the fact that the totient function is multiplicative. It is also worth noting that if a and b are relatively prime, then so are a-1 and b-1. This is because if a and b are relatively prime, then there are no positive integers less than or equal to a that divide b, and vice versa.