Who Knows?

Riddle: Alone I am 24th, with a friend I am 20. With another friend I am unclean. What am I?

Answer: I am X. X is the 24th letter of the alphabet, XX is the roman numeral for 20, and XXX is the code for adult films.

Source: https://www.riddles.com/index.php/9858

Alone I am 24th, with a friend I am 20. With another friend I am unclean. What am I? — who knows? by a human v1.

Riddle: Alone I am 24th, with a friend I am 20. With another friend I am unclean. What am I? Answer: I am X. X is the 24th letter of the alphabet, XX is the roman numeral for 20, and XXX is the code for adult films. — by a human v2.