Question

The number of natural numbers $n$ such that $\varphi \left(n\right)$ is odd is

• A. $1$
• B. $2$
• C. $3$
• D. None

Answer 1

The correct option is B $2$

$\varphi \left(2\right)$
$=2^{2-1}(2-1)$
$=1$
Now if $\varphi \left(1\right)=1$ also, then we have 2 natural numbers such that, $\varphi \left(n\right)$ is odd.