52 factorial
Here’s what a chap called Scott Czepiel has to say about the number of ways a deck of 52 cards can be shuffled, a topic I briefly mentioned almost a year ago:
This number is beyond astronomically large. I say beyond astronomically large because most numbers that we already consider to be astronomically large are mere infinitesmal fractions of this number.
Read the whole page. It takes you on a phenomenal mental journey.