Wouter,

OK I did a little digging around the web to try and find out how to show more cleanly what I did. I actually searched for "number of zeros in 100 factorial" via google.

Maybe I had done this calc in the past as part of my studies into Maths as part of my A levels and then deciding weather or not to take maths into a degree (I did not, I studied Computing, Management and software design).

I did essentially what is described here.

This is also worth a read

"interesting" to see what happens with 1,000,000! <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

More here

and here