When constructing compound numbers between 21 and 99, English grammar enforces a strict punctuation rule: the tens and units words must be linked with a hyphen. This applies directly to the entire family of numbers based on sixty.
Write them out systematically:
• 61: sixty-one
• 62: sixty-two
• 63: sixty-three
• 64: sixty-four
• 65: sixty-five
• 66: sixty-six
• 67: sixty-seven
• 68: sixty-eight
• 69: sixty-nine
Never write "sixty and one" or "sixty one" without the hyphen in standard written English. The conjunction "and" is reserved exclusively for connecting whole numbers to fractions or decimals (such as "sixty and a half"), or in British English, for connecting hundreds to tens (such as "one hundred and sixty"). Omitting the hyphen is one of the most common mechanical errors flagged in formal English editing.
