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.

When should numbers be hyphenated?

Always hyphenate adjectives that include a number when they appear in front of the noun they're modifying. This applies to both words and numerals: A six-foot ladder will be tall enough.

Do you hyphenate four thirty?

We use a hyphen to separate the hour from the minutes, as in four-thirty, but not if the expression of minutes requires a hyphen, as in four thirty-five.