Should You Hyphenate Numbers?

Always hyphenate the numbers 21 to 99 when writing them out as words: I have twenty-one pairs of novelty socks. ... However, it's only 21 to 99 that we hyphenate in these large numbers. Larger round numbers, such as “one hundred,” do not require a hyphen.

Are numbers supposed to be hyphenated?

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.

Do hyphens or dashes go between numbers?

Hyphens are used to separate groups of numbers, such as in telephone numbers or numbers of financial accounts. But for almost all other cases, the correct punctuation mark is an en dash, which indicates a range or a difference. A span of years (such as “2009–2012”) or any other time range includes an en dash.