Il numero romano MMMDCCCXCI nel sistema decimale vale: 3891.
MMMDCCCXCI in latino si scrive tria milia octingenti nonaginta unus,
mentre in italiano tremilaottocentonovantuno.
MMMDCCCLXXII, MMMDCCCLXXIII, MMMDCCCLXXIV, MMMDCCCLXXV, MMMDCCCLXXVI, MMMDCCCLXXVII, MMMDCCCLXXVIII, MMMDCCCLXXIX, MMMDCCCLXXX, MMMDCCCLXXXI, MMMDCCCLXXXII, MMMDCCCLXXXIII, MMMDCCCLXXXIV, MMMDCCCLXXXV, MMMDCCCLXXXVI, MMMDCCCLXXXVII, MMMDCCCLXXXVIII, MMMDCCCLXXXIX, MMMDCCCXC, MMMDCCCXCII, MMMDCCCXCIII, MMMDCCCXCIV, MMMDCCCXCV, MMMDCCCXCVI, MMMDCCCXCVII, MMMDCCCXCVIII, MMMDCCCXCIX, MMMCM, MMMCMI, MMMCMII, MMMCMIII, MMMCMIV, MMMCMV, MMMCMVI, MMMCMVII, MMMCMVIII, MMMCMIX, MMMCMX