19. $\overline{P Q Q P Q Q}, \overline{P Q P Q P Q}, \overline{Q P Q P Q P}, \overline{P P P P P P}, \overline{P P P Q Q Q}$ are five six-digit numbers, where the same letters represent the same digits, and different letters represent different digits. Regardless of what $P$ and $Q$ are, among these five six-digit numbers, $\qquad$ of them are definitely multiples of 7.
$4$