Find the number of odd proper divisors of `3^pxx6^mxx21^ndot`

Answer

(p+m+n+1)(n+1)-1

Explanation

`3^(p)6^(m)21^(n)=2^(m)3^(p+m+n)7^(n)`
Therefore, the required number of proper divisors is equal to the number of selections of any number of 3's and 7's `[because` for odd divisors 2 must not be selected ] and is given by (p+m+n+1) (n+1)-1.