The notation "φ(2)" refers to the value of the Euler's totient function, which counts the number of positive integers up to a given integer that are relatively prime to it. For the number 2, the only positive integer less than or equal to 2 that is relatively prime to it is 1. Therefore, φ(2) equals 1. In general, the Euler's totient function, denoted as φ(n), is significant in number theory and has applications in areas such as cryptography. It helps in understanding the properties of integers and their relationships, particularly in modular arithmetic.