Twenty-one

Twenty-one (21) is the natural number following twenty.

Twenty-one is a composite number, its proper divisors being 1, 3 and 7.

Twenty-one is/was also:

• a card game, also called vingt-et-un.
• Century 21[?] is a large real estate agent[?].
• before the Family Law Reform Act of 1969, the age of majority in England.
• In the United States, when one reaches 21, one gains the right to drink alcohol.
• The century that we are in currently is referred as the 21st century. It spans from 2001 to 2100[?].
• Pier21[?] was, from 1928 to 1971, the place where immigrants entered Canada. It was called the Gateway to Canada.

From this point on, there are articles for numbers at increments of tens up to one hundred.