>>507897851 (OP)The population of the Death Star varies depending on which version you're referring to and which source you consider (canon vs. Legends):
Canon (Disney-era, per โRogue One: Ultimate Visual Guideโ & other materials):
Death Star I (original one destroyed in A New Hope):
Crew: ~27,000 officers and enlisted
Stormtroopers: ~25,000
Support staff, pilots, technicians, etc.: ~250,000
Droids: ~400,000
Total (including droids): ~700,000
Legends (Expanded Universe, pre-Disney):
Death Star I (per Star Wars Technical Journal and Death Star novel):
Personnel (military and civilian): ~1.2 million
Droids: ~400,000
Troops: ~25,000โ50,000
Total: ~1.5โ2 million
Second Death Star (in Return of the Jedi) was incomplete but would've had similar or greater capacity once finished โ potentially millions more.