How do you put hyphens in numbers?

Hyphens are used in numbers when writing out compound numbers between twenty-one and ninety-nine, such as "twenty-one" or "eighty-five." They are also used to connect fractions when written in Words, like "two-thirds." However, hyphens are not needed for whole numbers or when numbers appear in numeral form. Always ensure to follow specific style guides, as they may have particular rules regarding hyphenation.