If every human alive for those 500 or so years shuffled a deck of cards, one deck per second, we’d end up with that many decks shuffled. That’s a huge number. 90,000,000,000,000,000,000.
And almost certainly, each one of those decks, post-shuffle, would be unique.
The number of possible permutations — arrangements, basically — of a deck of cards is 52! (“fifty two factorial”), or approximately 8×1067.
Excerpts from Now I Know article: