Definition:Giuga Number

Definition
Let $n$ be a positive integer.

$n$ is a Giuga number :
 * $\displaystyle \sum_{p \mathop \backslash n} \frac 1 p - \prod_{p \mathop \backslash n} \frac 1 p \in \Z_{\ge 0}$

where:
 * $p$ denotes a prime number
 * $p \mathop \backslash n$ therefore denotes that $p$ is a divisor of $n$.