How To Write Numbers in Full

The Quick Answer
When writing numbers in full, hyphenate all numbers between 21 and 99 (less those divisible by 10).

(Be aware that some grammar purists will expect you not to write the word and when writing numbers in full – unless you mean point. For them, and denotes the decimal point. In other words, they will take seven hundred and twenty-four as 700.24 not 724.)

Hyphens in Numbers

Regardless of where they appear within the whole number, all numbers between 21 and 99 (except 30, 40, 50, 60, 70, 80, and 90) should be hyphenated. (There is no need to use commas.)

Examples:
  • 51 (fifty-one )
  • 234 (two hundred and thirty-four )
  • 3,567 (three thousand five hundred and sixty-seven )
  • (note: no comma in the full version)

  • 44,120 (forty-four thousand one hundred and twenty )
  • 25,223 (twenty five thousand two hundred and twenty three )
  • (twenty five and twenty three should be hyphenated.)

  • 5,223 (five thousand, two hundred and twenty-three )
  • (comma not required)

  • 23,237,897 (twenty-three million two hundred and thirty-seven thousand eight hundred and ninety-seven )

See Also

Hyphens in compound adjectives Numbers as compound adjectives Starting sentences with numbers