Somebody watched Biden’s return from Delaware to DC on the 757 on flightaware. He posted on a YouTube video I was watching that the plane was squawking N/A not N2800 or N2900 if it was AF1. Mr.GG2 is a former pilot and he says he never heard of N/A.
The 'N' number is a bureau number not a 'squawk'. It is registered on the flight plan. Squawk is assigned by ATC, with your IFR clearance. 4 numbers. Military/Gov't don't have to squawk (use Transponder). Most do because you want to be an identified track for flight following, traffic separation etc. Most of my time I squawked 1200 (VFR) or had the transponder on standby (on but not sending). But most of my time was 500' or less.