let a number .... where 's are primes.
then the number of divisors of n is ...
now here ... =3
so one of is 3. this also means that only one of the is 2 and all others are 0.
so n= for some prime p; 2<n<49.
the only 's which qualify for the above condition are 2,3 and 5.
so the there numbers are 4,9 and 25.