The words for 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 are: one, two, three, four, five, six, seven, eight, nine and ten.

The words for 11, 12, 13, 14, 15, 16, 17, 18, 19 and 20 are: eleven, twelve, thirteen, fourteen, fifteen, sixteen, seventeen, eighteen, nineteen and twenty.

After twenty, there is a pattern to the words.  The tens place uses the words twenty, thirty, forty, fifty, sixty, seventy, eighty and ninety for 20, 30, 40, 50, 60, 70, 80 and 90.

If the ones place has more than zero, the word is formed by using the ten's place word, a hyphen, and then the ones place word.  Examples are:
    38 is thirty-eight
    84 is eighty-four
    25 is twenty-five