Euler function

The Euler function, often denoted as \(\phi(n)\), is also known as Euler's totient function. It counts the number of positive integers up to \(n\) that are coprime to \(n\). Two integers \(a\) and \(b\) are said to be coprime (or relatively prime) if their greatest common divisor (gcd) is 1. The function has both theoretical and practical applications in number theory and cryptography.