# Units in a ring?

How would I go about figuring out how many units are in Zeta 230?

#### Purslow

by zeta 230, do you mean the ring of intergers modulo 230? if so, the units are the invertible elements, ie 1, 3, 77, 7 , 33 ......

#### Drexel28

MHF Hall of Honor
by zeta 230, do you mean the ring of intergers modulo 230? if so, the units are the invertible elements, ie 1, 3, 77, 7 , 33 ......
Why not just say it? In general $$\displaystyle \text{card }(\mathbb{Z}/n\mathbb{Z})^{\times}=\varphi(n)$$ where $$\displaystyle \varphi(n)$$ is the number of things less than $$\displaystyle n$$ which are relatively prime to it.