If log 2 = 0.30103, the number of digits in 264 is:

Answer: Option C

$$\begin{array}{rl}& \log \left(2^{64}\right)\\ & =64\times \log 2\\ & =\left(64\times 0.30103\right)\\ & =19.26592\end{array}$$
Its characteristic is 19.
Hence, then number of digits in 2⁶⁴ is 20.