Hello,
Do you really mean to be modeling a 1.6 GW PV system?
I can't tell from your screenshot which inverter you are using. The inverter with the largest rated capacity in SAM's library is the SMA Technologies SC 2200, which has a maximum AC power rating of 2.079 MW. If you used that inverter in your 1.65 GWdc system with a 1.10 DC-to-AC ratio, you would need 1650 MWdc / 1.10 / 2.079 MWac = 721.5, which rounds up to 722 inverters.
Best regards,
Paul.