can anyone plz help

https://en.wikipedia.org/wiki/Euler%27s_totient_function

OK, young person, here is my best "guess"!

Since n is 2^100, or power of 2, all ODD numbers under 2^100 are "relatively prime" to it, which means: 2^100 / 2 =2^99   numbers that are relatively prime to 2^100.

thx!!!

For a positive integer $n,\ \phi(n)$ denotes the number of positive integers less than or equal to $n$ that are relatively prime to $n$.
What is $\phi(2^{100})$?

$\phi(n)$ is Euler's totient function

Formula, value for a prime power argument:

$\text{If $p$ is prime and $k \ge 1$, then $\\ \phi(p^k) = p^{k-1}(p-1)$ }$

$\begin{array}{|rcll|} \hline \mathbf{\phi(p^k)} &=& \mathbf{ p^{k-1}(p-1) } \\\\ \phi(2^{100}) &=& 2^{100-1}(2-1) \\ \mathbf{\phi(2^{100})} &=& \mathbf{2^{99}} \\ \hline \end{array}$