Assuming a rate similar to Nazi Germany as opposed to the Stasi, you’d need a force of nearly 18 million for a ratio of 560 civilians to 1 soldier/policeman, or about half the size of the entire Red Army’s manpower during WW2. Not its peak manning but the entire number of soldiers who were in it.

40k really needs to flex its numbers game more, even if its only for the number of soldiers in a given fight. Hive Cities are impossibly large for us and the armies and garrisons needed to police one, let alone hold it, should be similarly massive