No way this can be true. Facebook scaled primarily using CDNs like Akamai. Akamai is the largest CDN in the world and has no more than 300k-350k servers all over the world. It's one of the largest distributed system in the world. I worked there, so I know this for sure.
Facebook has recently been moving their data in house, but they do not have 830,000 servers. That's almost 3 times Akamai. At this point, Facebook would be more profitable letting people use their server infrastructure instead of using it for themselves.
Running Facebook over AWS is a CDN problem that was solved by Akamai!