 3-adic number

A 3-adic number belongs to the completion of $\mathbb{Q}$ for the p-adic absolute value with prime three. Its nonzero elements have the form $3^{k}u$, with $k\in \mathbb{Z}$ and $u\in {\mathbb{Z}}_3^{\times }$. The cube-class group of the 3-adic numbers is generated by the classes of $3$ and $4$.