Euler's totient function
Sign in to saveAlso known as phi function, Euler phi function, Euler totient function, totient function
function which gives the number of integers relatively prime to and not greater than its input
~30 min read
Encyclopedic overview
The first thousand values of φ(n). The points on the top line represent φ(p) when p is a prime number, which is p − 1.
In number theory, Euler's totient function counts the positive integers up to a given integer
Excerpted from Wikipedia’s “Euler's totient function” article, available under the CC BY-SA 4.0 licence.