וַיִּֽהְי֣וּ יְמֵי־אָדָ֗ם אַֽחֲרֵי֙ הוֹלִיד֣וֹ אֶת־שֵׁ֔ת שְׁמֹנֶ֥ה מֵאֹ֖ת שָׁנָ֑ה וַיּ֥וֹלֶד בָּנִ֖ים וּבָנֽוֹת׃
And the days of Adam after he begot Seth were eight hundred years; and he begot sons and daughters.
Read Kabbalistic (mystical) interpretations of Genesis 5:4: Zohar and classical Jewish mystical sources, free online.