Il numero romano CDXI nel sistema decimale vale: 411.
CDXI in latino si scrive quadringenti undecim,
mentre in italiano quattrocentoundici.
CCCXCII, CCCXCIII, CCCXCIV, CCCXCV, CCCXCVI, CCCXCVII, CCCXCVIII, CCCXCIX, CD, CDI, CDII, CDIII, CDIV, CDV, CDVI, CDVII, CDVIII, CDIX, CDX, CDXII, CDXIII, CDXIV, CDXV, CDXVI, CDXVII, CDXVIII, CDXIX, CDXX, CDXXI, CDXXII, CDXXIII, CDXXIV, CDXXV, CDXXVI, CDXXVII, CDXXVIII, CDXXIX, CDXXX