Is it "sixty third" or "sixty three" when writing an ordinal number?

If you mean the position in a sequence (ordinal), it is sixty-third (e.g., "the sixty-third person"). If you are just stating the number 63 (cardinal), it is sixty-three (e.g., "There are sixty-three apples"). The form depends on whether you need an ordinal (like 1st, 2nd, 3rd, 63rd) or a cardinal number (1, 2, 3, 63).