Google was spending $20 billion per year on its data centers in 2014 and now is spending about $30 billion per year.
Google used 5.7 terawatt-hours of electricity Google consumed in 2015 which is about 1 gigawatt of power. If each server used 200 watts then Google had 5 million servers in 2015.
In 2017, Google power usage has likely continued to increase and Google has some very energy efficient servers. It is highly likely that Google has over ten million servers.
Google’s global data centers have been using atomic clocks for database synchronization for close to ten years. The Spanner project was revealed over five years ago. Google began the spanner project over ten years ago. The Spanner database uses atomic clocks and GPS for transaction timing.