# README
Cube-full Divisors
A positive integer $n$ is considered cube-full, if for every prime $p$ that divides $n$, so does $p^3$. Note that $1$ is considered cube-full.
Let $s(n)$ be the function that counts the number of cube-full divisors of $n$. For example, $1$, $8$ and $16$ are the three cube-full divisors of $16$. Therefore, $s(16) = 3$.
Let $S(n)$ represent the summatory function of $s(n)$, that is $S(n) = \sum_{i=1}^n s(i)$.
You are given $S(16)=19$, $S(100)=126$ and $S(10000)=13344$.
Find $S(10^{18})$.
# Functions
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