וַֽיְהִ֗י כָּל־נֶ֛פֶשׁ יֹצְאֵ֥י יֶֽרֶךְ־יַעֲקֹ֖ב שִׁבְעִ֣ים נָ֑פֶשׁ וְיוֹסֵ֖ף הָיָ֥ה בְמִצְרָֽיִם׃
And all the souls that came out of the loins of Jacob were seventy souls; and Joseph was in Egypt already.
Read kabbalistic (mystical) interpretation of Exodus 1:5: and classical mystical sources.