Il numero romano MMDXCI nel sistema decimale vale: 2591.
MMDXCI in latino si scrive duo milia quingenti nonaginta unus,
mentre in italiano duemilacinquecentonovantuno.
MMDLXXII, MMDLXXIII, MMDLXXIV, MMDLXXV, MMDLXXVI, MMDLXXVII, MMDLXXVIII, MMDLXXIX, MMDLXXX, MMDLXXXI, MMDLXXXII, MMDLXXXIII, MMDLXXXIV, MMDLXXXV, MMDLXXXVI, MMDLXXXVII, MMDLXXXVIII, MMDLXXXIX, MMDXC, MMDXCII, MMDXCIII, MMDXCIV, MMDXCV, MMDXCVI, MMDXCVII, MMDXCVIII, MMDXCIX, MMDC, MMDCI, MMDCII, MMDCIII, MMDCIV, MMDCV, MMDCVI, MMDCVII, MMDCVIII, MMDCIX, MMDCX