Il numero romano MCCXCI nel sistema decimale vale: 1291.
MCCXCI in latino si scrive mille ducenti nonaginta unus,
mentre in italiano milleduecentonovantuno.
MCCLXXII, MCCLXXIII, MCCLXXIV, MCCLXXV, MCCLXXVI, MCCLXXVII, MCCLXXVIII, MCCLXXIX, MCCLXXX, MCCLXXXI, MCCLXXXII, MCCLXXXIII, MCCLXXXIV, MCCLXXXV, MCCLXXXVI, MCCLXXXVII, MCCLXXXVIII, MCCLXXXIX, MCCXC, MCCXCII, MCCXCIII, MCCXCIV, MCCXCV, MCCXCVI, MCCXCVII, MCCXCVIII, MCCXCIX, MCCC, MCCCI, MCCCII, MCCCIII, MCCCIV, MCCCV, MCCCVI, MCCCVII, MCCCVIII, MCCCIX, MCCCX