Il numero romano MDCCCXCI nel sistema decimale vale: 1891.
MDCCCXCI in latino si scrive mille octingenti nonaginta unus,
mentre in italiano milleottocentonovantuno.
MDCCCLXXII, MDCCCLXXIII, MDCCCLXXIV, MDCCCLXXV, MDCCCLXXVI, MDCCCLXXVII, MDCCCLXXVIII, MDCCCLXXIX, MDCCCLXXX, MDCCCLXXXI, MDCCCLXXXII, MDCCCLXXXIII, MDCCCLXXXIV, MDCCCLXXXV, MDCCCLXXXVI, MDCCCLXXXVII, MDCCCLXXXVIII, MDCCCLXXXIX, MDCCCXC, MDCCCXCII, MDCCCXCIII, MDCCCXCIV, MDCCCXCV, MDCCCXCVI, MDCCCXCVII, MDCCCXCVIII, MDCCCXCIX, MCM, MCMI, MCMII, MCMIII, MCMIV, MCMV, MCMVI, MCMVII, MCMVIII, MCMIX, MCMX