literally: “booze number” / a number composed by a sequence of the same digit
You know why Schnapszahl is something like the perfect German word? Because it combines two of Germans’ greatest passions: the passion for booze—and the passion for order.
The term refers to a number that consists of various instances of the same digit, like 11, 555 and 7777. And of course, the infamous “number of the beast” is a Schnapszahl as well. The magic of Schnapszahlen has also led to crowded registry offices everywhere in the world on dates like 9/9/99 or 11/11/11. Maybe that is because women want to make it easier for their idiot husbands to remember their anniversary.
The reason why such a number is called a “booze number” is probably linked to some dice games where a player who throws a double has to pay the next round. It might also have to do with the “double vision” phenomenon that you experience after your eleventh Jägermeister.