The only word I can think of is "POLO!!", as in the pool game Marco Polo.
Some 10 letter P words:partialityparticularpermissionpersonallyprecautionpresupposepronouncedproportionprejudicedproportionprefermentprepaymentpreachmentplacementspracticingpercentileproductivepermissiveprovisionsprotectionprovention
preposterous
procrastinate
Primper.
pepperoni
pi
phenomenal
There are no 23 letter words in the English language starting with the letter p.
prize
plaza
Plundering
Pepsi