9. Let $M=\{1,2, \cdots, 2005\}, A$ be a subset of $M$ and satisfy the condition: if $x \in A$ then $15 x \notin A$, then the maximum number of elements in $A$ is $\qquad$
9. 1880 To ensure that when $x \in A$, $15 x \notin A$, it is sufficient that $15 x > 2005$, which means $x \geqslant 134$. Therefore, $A$ can include $\{134,135, \cdots, 2005\}$. Additionally, to ensure that when $x \in A$, $15 x \notin A$ and $x < 9$, $A$ can also include $\{1,2, \cdots, 8\}$. Taking the subset $A=\{1,2, \cdots, 8\} \cup \{134,135, \cdots, 2005\}$ of $M$, it satisfies the conditions, and the number of elements in $A$ is $|A|=1880$. It is clear that the number of elements in such an $A$ is the maximum.