need to find the cardinality of the set of all prime factors of 120

Will it be 16? Since the set of all prime factors of 120 will always have 16 elements i.e { 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 24, 30, 40, 60, 120 }

Or is this a trick question and requires a proof to answer?