Question 180
Determine all integers $n \ge 2$, having at least four positive divisors, with the property that for any two distinct divisors $d_1$ and $d_2$ of $n$, such that $1 \lt d_1 \lt d_2 \lt n$, the number $d_2 - d_1$ is also a divisor of $n$.
Lucian Petrescu
Lucian Petrescu