We want to find the exponent to which 4 must be raised to get 64.
Writing this as a logarithm, we have $\log_4 64 = x$, where $4^x = 64$.
Since $4^3 = 64$, we have $x = \boxed{3}$.
The answer is: 3
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
What is the value of $\log_4 64$?

### Answer:
