If a number is represented in the form \(p^x * q^y * r^z ..\) where p,q,r and x, y , z are positive integers
Total number of factors = (x+1)(y+1)(z+1)
Is given that x consists of total 16 factor.
16 = \(2^4\), thus the total number of factors can be formed by multiplying the 2's in any order.
Lets assume that the number is N
For ex-
16 could have been formed by multiplying 4 * 4, or 2 * 8 or may be just 16* 1.
Option analysis
A) 31
N = \(p^{15}\)
Total factors of N will be 16.
\(N ^ 2 \) = \(p^{(2*15)}\)
Total factors of \(N^2\) will be 31.
Hence this is possible
B) 45
N = \(p^1 * q^7\)
Total factors N will be 2 * 8 = 16.
\(N ^ 2 \) =\(p^2 * q^{14}\)
Total factors of \(N^{2}\) will be 3 * 15 = 45.
Hence this is possible
C) 49
N = \(p^3 * q^3\)
Total factors N will be 4 * 4 = 16.
\(N ^ 2 \) =\(p^6 * q^{6}\)
Total factors of \(N^{2}\) will be 7 *7 = 49.
Hence this is possible
D) 63
N = \(p^1 * q^1 * r^3\)
Total factors N will be 2 * 2 * 4 = 16.
\(N ^ 2 \) =\(p^2 * q^2 * r^6\)
Total factors of \(N^{2}\) will be 3 * 3 * 7= 63.
Hence this is possible
D) 87
Only remaining option
IMO - E