How to write numbers in full.
 
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 )
 
FORTY NOT FOURTY 

The number 40 is spelt forty and not fourty.

WRITING AND

Be aware that some grammar purists (particularly in America) state that and is only used when writing numbers to denote a decimal point.

In other words, if you wrote one hundred and one, they would take this to mean 100.1 and not 101.

POINT OF INTEREST – NO A BETWEEN 1 AND 999

Interestingly, if you adopt the rule above regarding and and start writing out all the numbers from 1 upwards, you will reach 1000 before you use the letter a.
 


See also:

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