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.