Sorry about that. 1 1/4 Billion.
That number floats wildly even in their out accounting (1.0-1.5 billion, so they claim).
There are millions of so-called muslims in this world who have no choice in this matter. They are not permitted a freedom of religion. Some muslim nations prohibit the practice and texts of all other religious beliefs. Even in some theocratic nations where other faiths are permitted, persons who were born to a muslim father are not permitted to leave the cult under penalty of death.
When the US government was busy making sure that terrorists held prisoner at Gitmo got korans and halal meals, they SHOULD have been notifying the prisoners that they were FREE to practice any religious tradition, not just Islam.