Question

The number of divisors of $N=2^7.3^3.5^4$ divisible by 6 but not by 15 is

• A. 24
• B. 21
• C. 30
• D. 60

Answer 1

The correct option is B 21

$N=2^7{.3}^3{.5}^4$
number of divisors divisible by 6 and not by 15 can be written as
$=2.3\left(2^6{.3}^2{.5}^4\right)$ total ways $=7\times 3=21$