quintus-dĕcĭmus — Lewis & Short
quintus-dĕcĭmus, a, um, num. adj.,
locus,Cic. Inv. 1, 54, 105:
quintisdecimis castris,Liv. 45, 33 fin.:
in libro quintodecimo,Gell. 1, 16, 11;
often separately: quinto decimo Kal. Dec.,Col. 11, 2, 88;
and sometimes in reverse order: anno decimo quinto,Eutr. 1, 19.