Il numero romano CDXXIII nel sistema decimale vale: 423.
CDXXIII in latino si scrive quadringenti viginti tres,
mentre in italiano quattrocentoventitré.
CDIV, CDV, CDVI, CDVII, CDVIII, CDIX, CDX, CDXI, CDXII, CDXIII, CDXIV, CDXV, CDXVI, CDXVII, CDXVIII, CDXIX, CDXX, CDXXI, CDXXII, CDXXIV, CDXXV, CDXXVI, CDXXVII, CDXXVIII, CDXXIX, CDXXX, CDXXXI, CDXXXII, CDXXXIII, CDXXXIV, CDXXXV, CDXXXVI, CDXXXVII, CDXXXVIII, CDXXXIX, CDXL, CDXLI, CDXLII