That figure irritates the bejesus out of me everyday as it is a complete falsehood which has been repeated enough times that everybody now quotes it as gospel, they dont have 659 million fans or anywhere close to that, that figure was generated by a marketing company who used the metric of anyone that has typed united into a search bar would be classed as a united fan, so even as a city fan if you had typed city vs united tickets into the search bar you would be classed as showing interest in the rags and therefore be classed as a fan, its just another in a long line of myths that surround that shambles of a club propped up by a supportive media who are happy to perpetuate their bullshit.