Divisibility

Definition

If $n$ and $d$ are integers and $d\ne 0$, then $n$ is divisible by $d$ iff $n$ equals $d$ times some integer

Notation

$d|n$ means ”$d$ divides $n$”, if $n,d\in \mathbb{Z}$ and $d\ne 0$ $d|n\iff \exists k\in \mathbb{Z}$ such that $n=dk$