Il numero romano MMCXCI nel sistema decimale vale: 2191.
MMCXCI in latino si scrive duo milia centum nonaginta unus,
mentre in italiano duemilacentonovantuno.
MMCLXXII, MMCLXXIII, MMCLXXIV, MMCLXXV, MMCLXXVI, MMCLXXVII, MMCLXXVIII, MMCLXXIX, MMCLXXX, MMCLXXXI, MMCLXXXII, MMCLXXXIII, MMCLXXXIV, MMCLXXXV, MMCLXXXVI, MMCLXXXVII, MMCLXXXVIII, MMCLXXXIX, MMCXC, MMCXCII, MMCXCIII, MMCXCIV, MMCXCV, MMCXCVI, MMCXCVII, MMCXCVIII, MMCXCIX, MMCC, MMCCI, MMCCII, MMCCIII, MMCCIV, MMCCV, MMCCVI, MMCCVII, MMCCVIII, MMCCIX, MMCCX