The notation "φ(4)" refers to the value of the Euler's totient function, denoted as φ(n), which counts the number of positive integers up to n that are relatively prime to n. In this case, φ(4) calculates how many integers from 1 to 4 do not share any common factors with 4 other than 1. To find φ(4), we identify the integers 1, 2, 3, and 4. The integers that are relatively prime to 4 are 1 and 3. Therefore, φ(4) equals 2, indicating that there are two integers less than or equal to 4 that are coprime to it.