Il numero romano MDXCI nel sistema decimale vale: 1591.
MDXCI in latino si scrive mille quingenti nonaginta unus,
mentre in italiano millecinquecentonovantuno.
MDLXXII, MDLXXIII, MDLXXIV, MDLXXV, MDLXXVI, MDLXXVII, MDLXXVIII, MDLXXIX, MDLXXX, MDLXXXI, MDLXXXII, MDLXXXIII, MDLXXXIV, MDLXXXV, MDLXXXVI, MDLXXXVII, MDLXXXVIII, MDLXXXIX, MDXC, MDXCII, MDXCIII, MDXCIV, MDXCV, MDXCVI, MDXCVII, MDXCVIII, MDXCIX, MDC, MDCI, MDCII, MDCIII, MDCIV, MDCV, MDCVI, MDCVII, MDCVIII, MDCIX, MDCX