The number of odd proper divisors of 5040 , is
(a) 12
(b) 10
(c) 11
(d) none of these

We have,
( 5040=2^{4} times 3^{2} times 5 times 7 )
( therefore quad ) Number of odd proper divisors
= Number of ways of selecting any number of ( 3^{text {'s }} ) out
two ( 3^{prime prime}, ) any number of ( 5^{prime s} ) and ( 7^{prime prime} )
[
=(2+1)(1+1)(1+1)-1=11
]