The notation "φ(10)" refers to the Euler's totient function, which counts the number of positive integers up to a given integer that are relatively prime to it. In this case, φ(10) calculates how many integers from 1 to 10 do not share any factors with 10 other than 1. To find φ(10), we first identify the prime factorization of 10, which is 2 × 5. The integers that are relatively prime to 10 within this range are 1, 3, 7, 9. Therefore, φ(10) equals 4, indicating that there are four integers less than or equal to 10 that are coprime to it.