17,151. This included 8,954 Navy personnel, 6,021 Marines, 1,699 Naval Intelligence agents, and 477 civilians
However we know there are also and unknown number of army and air force personnel aboard as well. So how many are there/ what's Infinity's max capacity. Well I think the answer can be determined via analyzing the number of escape vessels Infinity has. It has 8,900 SKT-29 Class-8 Enclosed Heavy Lifeboats/Controlled and 12,750 RLT-85 Emergency Shuttlepods. The lifeboats can hold 9 people each including the pilot so around 80,100 (assuming they can each hold as many as the Autumn's lifeboats), Shuttlepods are presumably larger and can likely hold lets say 17 people, which brings us to around 216,750.
Well Stark are you saying Infinity has a max complement of 300,000? No, as awesome as that would be. Modern Naval standards for the US Navy require military vessels to have at least 4 times as many seats as personnel aboard a vessel. So lets use that figure. We still get a whopping 74,212 individuals making the comment that Infinity's as large as a city backed by the population of a small city. That means that aside from the 6,000 marines there could have been as many as 50,000 army personnel aboard as well. Sounds more like the culmination of human achievement to me.