How to write numbers in words
0 – 12 have special names: zero, one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve.
13 – 19 end in -teen: thirteen, fourteen, fifteen, sixteen, seventeen, eighteen, nineteen.
20 – 90 (the tens) end in -ty: twenty, thirty, forty, fifty, sixty, seventy, eighty, ninety. Watch out for forty (no “u”) and fifty (not “fivety”).
21 – 99 use a hyphen between the tens and the units: twenty-one, forty-five, ninety-nine.
100 – 999: one hundred, two hundred… In British English we add and before the last part: one hundred and twenty-three.
1,000 – 999,999: one thousand, ten thousand, twenty thousand, one hundred thousand.
1,000,000 +: one million, ten million, one hundred million.
Handy tip: the number 17 is seventeen, but 70 is seventy. Listen for -teen (13–19) versus -ty (20–90).