Nick's the new owner of the swanky $6.5 million crib in Beverly Hills Post Office -- for all you out-of-towners, it's adjacent to Bev Hills and shares the same zip code -- who popped the question to Priyanka 3 months later.

The house is pretty incredible -- 5 bedrooms, 4.5 bathrooms sit on 4,129 square feet. The pad's an architectural masterpiece ... featuring expansive canyon views, a floating guest wing and an extended wood terrace that wraps around the swimming pool.

Fun fact -- there are lots of homes on L.A. mountainsides where the backyards are cantilevered and seem to be floating. They're super reinforced to withstand earthquakes ... hopefully.

Brian Courville from Pacific Union was the listing agent and Carl Gambino from Westside Estate Agency repped Nick.