Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
invertĭbĭlĭtas, ātis, f. [2. in-verto], unchangeableness (eccl. Lat.): incommutabilitas, atque, ut ita dicam, invertibilitas, Aug. de Mor. Eccl. 13, 28.