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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.

Factorials: Level 2 Challenges

Which of these numbers is a perfect square?

What is the product of all positive odd integers less than $$10000$$?

$\large 1 \cdot 1! + 2\cdot 2! + 3\cdot 3! + \cdots + 25\cdot 25! = \, ?$

Which is greater?

$300! \text{ or } 100^{300} ?$

Given that $$13!= 13 \times 12 \times 11 \times \cdot \cdot \cdot \times 2 \times 1 = 6227020800$$, it can be seen that $$13!$$ contains two trailing zeroes.

How many trailing zeroes does $$1000!$$ contain?

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