For how many integers $a$ satisfying $1 \le a \le 23$ is it true that $a^{-1} \equiv a \pmod{24}$?
Question:
For how many integers $a$ satisfying $1 \le a \le 23$ is it true that $a^{-1} \equiv a \pmod{24}$?
Answer:
Let's think step by step.

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For how many integers $a$ satisfying $1 \le a \le 23$ is it true that $a^{-1} \equiv a \pmod{24}$?
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