The 617-573 prefix is in Boston, MA.
Belmont, MA, is in area codes 617 and 857.
The 312 area code is used for downtown Chicago. It is is unusual in that it is completely surrounds by another area code which is 773 and covers the rest of Chicago.
It is difficult to find statistics on the exact geographic area corresponding to an area code, but the two candidates are area code 312 in downtown Chicago and area code 213 in downtown Los Angeles. Area code 312 in downtown Chicago is overlaid with area code 872, which also overlays area code 773 in the rest of Chicago.
US area code 872 is Chicago, IL, overlaying 312 and 773.
There are a few different area codes for Chicago. They are 630,312,847,815 and a few others.
Area code 847 is the suburbs north of Chicago, including Evanston and Skokie. It is overlaid with area code 224.
Area code 312 is downtown Chicago. It includes the Chicago Loop and the immediate area around it. The 312-273 prefix is mostly for wireless users (cell phones), but may also include some landline numbers. Area code 773, which serves the rest of Chicago, completely surrounds area code 312; area code 872 is an overlay on both 312 and 773, serving the entire city of Chicago, but not the suburbs.
In 2009 the area code 773 stopped being in use for the city of Chicago. Instead the state employed a wider area code for the city and its suburbs rather than using two or more area codes for the full area.
The area of Dourou is 617 square kilometers.
It is 617 miles according to Google Maps.
Area code 773 is an area code for Chicago, Illinois. The city was given this area code on October 12'th, 1996. Before this code the area code was 312, for the whole city until 708 was created for the suburbs only.