Find the number of trailing zeroes in
Notation: denotes the double factorial function
The answer is 0.
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1 solution
2 0 1 7 2 0 1 7 ! ! = 2 0 1 7 2 0 1 7 × 2 0 1 7 2 0 1 5 × 2 0 1 7 2 0 1 5 × 2 0 1 7 2 0 1 3 × ⋯ × 7 × 5 × 3 × 1
∵ All the numbers in the product are odd, like 20172017 , 20172015 , etc. and a number has trailing zeroes if it has both 2 and 5 as a factor but, 2 0 1 7 2 0 1 7 ! ! doesn't has 2 as a factor
∴ There are no trailing zeroes.