How many ping pong balls fit in an olympic swimming pool?

Using the minimum requirements for an "Olympic" size swimming pool of 50m long, 25m wide and 2m deep, volume in mm is 2,500,000,000,000. An ITTF approved table tennis ball is 40mm. If they stack perfectly in the pool, they will stack just like if they were cubes. The volume of a cube the same size is 64,000mm. If stacked perfectly 390,625,000 ping pong balls should fit into an olympic swimming pool.