Consider $x$ to be composite, let $x$ has more than one prime factor then we can write $x=p_1^{a_1}p_2^{a_2}..p_j^{a_j}..p_n^{a_n}$, where $a_i\ge 1$ and all $p_i$ are distinct primes, $1\le j<n$ so let $a=p_1^{a_1}p_2^{a_2}..p_j^{a_j}$ and $b=p_j^{a_j}..p_n^{a_n}$, then we have $x|ab$ but $x$ neither divide $a$ nor $b$, contradiction!! so $x$ has exactly one prime factor, say $x=p^a$, so if $a>1$, then we have $x=p.p^{a-1}=ab$, but $x$ does not divide $p$ or $p^{a-1}$ , contradiction! hence $x=p$ for some prime, but $x>1$ so $x$ is prime and hence number of positive integer divide $x$ is 2, $1$ and $x$