Lewis & Short

trīginta (freq. written ), num. adj. indecl. [τριάκοντα], thirty: minae, Plaut. Curc. 2, 3, 65: Romulus cum septem et triginta regnavisset annos, Cic. Rep. 2, 10, 18; Liv. 1, 21, 6: triginta magnos orbīs explebit, Verg. A. 1, 269: conjectus in carcerem triginta jussu tyrannorum, of the thirty tyrants (in Athens), Cic. Tusc. 1, 40, 96; cf. id. Leg. 1, 15, 42; id. Rep. 3, 32, 44; 1, 28, 44 Mos. N. cr.