I recently got a business call from a 720 number and wondered if this code covers only Denver or also surrounding Colorado suburbs. Curious how locals usually recognize these numbers.

The 720 area code covers Denver and many surrounding suburbs across the metro area, not just the city itself. Places like Aurora, Lakewood, Boulder, and Westminster can all use 720 numbers. A lot of locals see it as a normal Colorado metro code alongside 303. If you want to check where a specific number may be registered, you can look it uphere before calling back.