All 15 have the ORDAINED priesthood office of apostle. They are SET APART as members of the Q12 and SUSTAINED as prophets, seers and revelators. Those last three titles describe gifts and functions, not priesthood offices. The three in the quorum of the First Presidency remain ordained apostles but are SET APART as the presiding high priests over the Melchizedek Priesthood. This is how they preside over the Q12. The correct term for the presiding high priest is President of the Church. Calling him "the Prophet" is an everyday usage, not a priesthood office.