This article is about the number 21. For the year, see 21
Twenty-one is a number. It comes between twenty and twenty-two, and is an odd number. It is divisible by 1, 3, 7, and 21.
Twenty-one is also a name of a popular card game and is the age at which people in the United States can buy alcoholic drinks.
In Roman numerals, 21 is written as XXI.