$20!$ has 19 digits, the last 18 of which are 432902008176640000. What is the first digit?
Question:
$20!$ has 19 digits, the last 18 of which are 432902008176640000. What is the first digit?
Answer:
Let's think step by step.

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$20!$ has 19 digits, the last 18 of which are 432902008176640000. What is the first digit?
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