I'm selling my iphone 6, If i go to the settings and delete all the information on the phone?

If I go to settings and wipe the phone clean, is there any way the buyer can get that information back through Icloud or something. I have often texting very personal information like my social security banking info and personal life information too. I would not want anyone but me to see this info. Is there any chance he can get this back if I format it?

Yeea