You should always hyphenate numbers when you are describing compound numbers between 21 and 99 (except 30, 40, 50, 60, 70, 80 and 90). A compound number is any number that consists of two words; for example, eighty-eight, twenty-two, forty-nine. Numbers higher than 99 do not need a hyphen.

Does the number twenty one have a hyphen?

Use a hyphen when writing two-word numbers from twenty-one to ninety-nine (inclusive) as words. But don't use a hyphen for hundreds, thousands, millions and billions.

Is twenty first hyphenated?

Compound numerals

Hyphenate compound cardinal and ordinal numerals from twenty-one (twenty-first) to ninety-nine (ninety-ninth) when they are written out: There are twenty-nine members on the committee.