\begin{definition}[Definition:Giuga Number]
Let $n$ be a positive integer.
$n$ is a '''Giuga number''' {{iff}}:
:$\ds \sum_{p \mathop \divides n} \frac 1 p - \prod_{p \mathop \divides n} \frac 1 p \in \Z_{\ge 0}$
where:
:$p$ denotes a prime number
:$p \divides n$ therefore denotes that $p$ is a divisor of $n$.
\end{definition}