1. The problem asks: Which number equals $\log_a a$? 2. Recall the definition of logarithms: $\log_a b = c$ means $a^c = b$. 3. Applying this to $\log_a a$, we want to find $c$ such that $a^c = a$. 4. Since $a^1 = a$, it follows that $c = 1$. 5. Therefore, $\log_a a = 1$. This is a fundamental property of logarithms: the log base $a$ of $a$ is always 1.