Euler's Totient Function

Euler's Totient Function, often denoted as φ(n), measures the count of positive integers up to n that are relatively prime to n. In simpler terms, it tells you how many numbers less than n do not share any factors with n other than 1. For example, φ(9) is 6, meaning there are six numbers (1, 2, 4, 5, 7, 8) under 9 that do not have 3 as a common factor. This function is significant in number theory and plays a crucial role in cryptography, particularly in algorithms like RSA, which rely on the properties of primes and coprimes.