Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
undēsexaginta, num. adj. [unus-desexaginta], fifty-nine: undesexaginta (Carthaginiensium) vivi capti, Liv. 23, 37, 6: dies, Plin. 36, 15, 24, § 122.