  Let $K = \Q(\theta)$ be an algebraic number field with $\theta$ satisfying an
irreducible polynomial $x^{9} - a$ over the field $\Q$ of rationals and $\Z_K$
denote the ring of algebraic integers of $K$. In this article, we provide the
exact power of each prime which divides the index of the subgroup $\Z[\theta]$
in $\Z_K$. Further, we give a $p$-integral basis of $K$ for each prime $p$.
These $p$-integral bases lead to a construction of an integral basis of $K$
which is illustrated with examples.
