Question 199
Find all positive integers $n$ which satisfy the following two conditions:
(i) $n$ has at least four different positive divisors;
(ii) for any divisors $a$ and $b$ of $n$ satisfying $1 \lt a \lt b \lt n$, the number $b - a$ divides $n$.
(i) $n$ has at least four different positive divisors;
(ii) for any divisors $a$ and $b$ of $n$ satisfying $1 \lt a \lt b \lt n$, the number $b - a$ divides $n$.