The approximate number of legal chess positions is called the Shannon Number (after mathematician Claude Shannon) and is 10 to the 43rd power; that is a 1 with 43 zeroes after it! This is only legal chess positions; counting all possible chess games would be far larger of a number (due to things like repetition of moves for example; although the number would not be infinite because of draw by repetition and the 50 move rule).
p.s. the facts do not need to be chess-related, but I thought a chess fact was nice since this is a chess site after all
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