$64$ can be written as:

The correct option is A

$2^6$

Given number: $64$

Now, prime factorisation of $64$ is

$64=2\times 2\times 2\times 2\times 2\times 2$

We know that, $a^n=a\times a\times a\times a\times a\times a.....uptonterms$

Therefore,

$$\begin{gathered} 64=2\times 2\times 2\times 2\times 2\times 2 \\ =2^6 \end{gathered}$$

Hence, option (A) is correct answer.