21 - Number of years that the previous 9 Pakistani Test centuries against Australia took.
Shows the level of complete dominance and break from history that this series has been for Pakistan. They are now on verge of a 3rd successive Test win against Australia after having lost the preceding 13 in a row against them.
Unrelated but comparable factoid.
6 - India's medal haul in 2012 London Games
7 - The number of previous Olympics (from 1984 - 2008) in which India got 6 medals combined.