Il numero romano MDCCCI nel sistema decimale vale: 1801.
MDCCCI in latino si scrive mille octingenti unus,
mentre in italiano milleottocentouno.
MDCCLXXXII, MDCCLXXXIII, MDCCLXXXIV, MDCCLXXXV, MDCCLXXXVI, MDCCLXXXVII, MDCCLXXXVIII, MDCCLXXXIX, MDCCXC, MDCCXCI, MDCCXCII, MDCCXCIII, MDCCXCIV, MDCCXCV, MDCCXCVI, MDCCXCVII, MDCCXCVIII, MDCCXCIX, MDCCC, MDCCCII, MDCCCIII, MDCCCIV, MDCCCV, MDCCCVI, MDCCCVII, MDCCCVIII, MDCCCIX, MDCCCX, MDCCCXI, MDCCCXII, MDCCCXIII, MDCCCXIV, MDCCCXV, MDCCCXVI, MDCCCXVII, MDCCCXVIII, MDCCCXIX, MDCCCXX