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# Factorials

2! = 2, 3! = 3*2, 4! = 4*3*2… and 100! is a lot better than writing out 158 digits. 90! is the largest factorial that can fit in a tweet.

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How many of the following 99 integers are primes?

\[\begin{array} &100!+2, &100!+3, &100!+4, &\ldots, &100!+100\end{array}\]

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Chung Kevin**

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How many positive integers are divisors of \(21!\) but are not divisors of \(20!\)?

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Janardhanan Sivaramakr...**

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Find the remainder when \(70!\) is divided by \(5183\).

Note: Don't use a computational device!

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Krishna Ar**

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\[\large \lim_{n \rightarrow \infty} { 2n \choose n } ^ { \frac{1}{n} } = \ ?\]

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Calvin Lin**

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Samir Khan**

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