JS can only handle number less than 10 ^ 16 before switching to exponentiation form.
You have two options:

• find a way to not generate such huge numbers: you're only interested by the zeroes at the end of this number afterwards.
• switch to a language that handle infinite digits arithmetic (yes this kata is terribly easy in Python)

If you would like to count something, you will not always need to generate the full result first.

A viable suggestion for solvers might be try to work out n = 1, 2, 3, 4 to something like 15 (not too big), and guess the pattern / try to find out what is really affecting the solution.