The answer is twenty-one.
Gretchen and Elliott just got back from New York, so “21” is referring to 21 Club which is a prohibition-era speakeasy that opened in 1922. Laden with contraptions and levers that hid full bars and opened chutes to pour alcohol out, the owners were never caught by the police.
Since Prohibition was repealed, the establishment has been frequented by Presidents (Franklin Delano Roosevelt and Barack Obama) to celebrities (George Clooney and Robert DeNiro).
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