That is a crazy number and in many cases would surpass whole countries population. At the current level of 8.58 million people is more bearable, but as more and more people migrate to metropoles who knows what would be the final number of it. And there is a clear movement towards that, thus the cities need to become smarter in order to cope with such complex logistics and utilities. Probably AI can help with those optimizations after it evolves itself to better levels.