A number of 8 million (give or take) is the official estimate. This doesn't include unlicenced knockoffs, such as the Chinese CQ-556, Iranian DIO-S5.56, Sudanese Terab, or Philippine Armada.
Well, since pizza has been around about 200 years, and 1051200 pizzas are made a year. All you have to do is multiply them together to get the grand total of 210240000 pizzas made all time. Pizzas...