Totative
In number theory, a totative of a given positive integer is an integer such that and is coprime to . Euler's totient function φ counts the number of totatives of n. The totatives under multiplication modulo n form the Multiplicative group of [integers modulo n|multiplicative group of integers modulo n].
Distribution
The distribution of totatives has been a subject of study. Paul Erdős conjectured that, writing the totatives of n asthe mean square gap satisfies
for some constant C, and this was proven by Bob Vaughan and Hugh [Montgomery (mathematician)|Hugh Montgomery].