sex·ag·e·nar·y 
(sĕk-săjə-nĕr′ē)
(sĕk-săjə-nĕr′ē)adj.
1. Relating to or proceeding by sixties.
2. Sexagenarian.
n. pl. sex·ag·e·nar·ies
A sexagenarian.
[Latin sexāgēnārius, from sexāgēnī, sixty each, from sexāgintā, sixty : sex, six; see SEX- + -gintā, ten times; see dek in the Appendix of Indo-European roots.]