Except for Philippians, Thessalonians and Philemon, Paul’s letters began with him introducing himself this way. Also, if you understand how God uses numbers, you know that he would never have 13 Apostles. The number 13 is associated in Scripture with rebellion, apostasy, defection, corruption, disintegration, and revolution.

In many early Christian texts Mary Magdalene was the 13h disciple. She was the one who the lord imparted special wisdom to her to be transmitted to the other twelve. She caused a lot of antagonism too, especially with Peter who once aske the lord to send her away and complained that he used to kiss her often on the mouth.