There are 39 13-letter words that start with 'ap'.
Note: These 39 13-letter words that start with 'ap' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with app, apo, aph, api, apa, ape, apr, apt, apl, apn, aps, apy.
3-letter words start with 'ap' (4)