(number theory) The function that calculates the total number of integers below a given integer that are coprime to it.

Counts integers coprime to n.

In number theory, Jordan's totient function, denoted as , where is a positive integer, is a function of a positive integer, , that equals the number of -tuples of positive integers that are less than or equal to and that together with form a coprime set of integers.

In number theory, a perfect totient number is an integer that is equal to the sum of its iterated totients.