Cardinal Number

Cardinal numerals answer the question 'how many?'. Numerals from 'one' to 'twelve', as well as 'hundred, thousand, million, billion', are fixed words. Numerals from 13 to 19 are derived from corresponding simple ones by adding the suffix -teen (some stems are modified): thirteen = 13; fourteen = 14; fifteen = 15; sixteen = 16; seventeen = 17; eighteen = 18; nineteen = 19. The numerals that are multiples of 10 are formed by addition of the suffix -ty to the number of tens, with occasional modifications: twenty = 20; thirty = 30; forty = 40; fifty = 50; sixty = 60; seventy = 70; eighty = 80; ninety = 90.
Complex numerals are formed by putting the first two described types together in order from left to right (tens and units are written with a hyphen). The words 'hundred, thousand, million, billion', etc., are always used in the singular form.

Example:

one hundred twenty-five = 125; five hundred seventy-two = 572; two thousand six hundred fifty-one = 2,651; three million four hundred ninety-six thousand seven hundred eighty-three = 3,496,783.