Find all positive integers
which satisfy the following tow conditions:
(a)
has at least four different positive divisors;
(b) for any divisors
and
of
satisfying
, the number
divides
.
%V0
Find all positive integers $n$ which satisfy the following tow conditions:
(a) $n$ has at least four different positive divisors;
(b) for any divisors $a$ and $b$ of $n$ satisfying $1<a<b<n$, the number $b-a$ divides $n$.
Školjka