Il numero romano MCXCI nel sistema decimale vale: 1191.
MCXCI in latino si scrive mille centum nonaginta unus,
mentre in italiano millecentonovantuno.
MCLXXII, MCLXXIII, MCLXXIV, MCLXXV, MCLXXVI, MCLXXVII, MCLXXVIII, MCLXXIX, MCLXXX, MCLXXXI, MCLXXXII, MCLXXXIII, MCLXXXIV, MCLXXXV, MCLXXXVI, MCLXXXVII, MCLXXXVIII, MCLXXXIX, MCXC, MCXCII, MCXCIII, MCXCIV, MCXCV, MCXCVI, MCXCVII, MCXCVIII, MCXCIX, MCC, MCCI, MCCII, MCCIII, MCCIV, MCCV, MCCVI, MCCVII, MCCVIII, MCCIX, MCCX