וַֽיְהִי֙ כָּל־יְמֵי־לֶ֔מֶךְ שֶׁ֤בַע וְשִׁבְעִים֙ שָׁנָ֔ה וּשְׁבַ֥ע מֵא֖וֹת שָׁנָ֑ה וַיָּמֹֽת׃ (ס)
And all the days of Lamech were seven hundred seventy and seven years; and he died.
Read Kabbalistic (mystical) interpretations of Genesis 5:31: Zohar and classical Jewish mystical sources, free online.