sixty (adj., n.)

"1 more than fifty-nine, twice thirty; the number which is one more than fifty-nine; a symbol representing this number;" Old English sixtig, from siex (see six) + -tig (see -ty (1)). Similar formation in Old Norse sextugr, sextögr, sextigir, Old Frisian sextich, Middle Dutch sestig, Dutch zestig, Old High German sehszug, German sechzig. Phrase sixty-four dollar question is attested from 1942, from a radio quiz show where that was the top prize.