Cities in area code 631

54 localities · NANPA data, current as of July 28, 2026.

Area code 631 serves 54 localities in New York, led by Brentwood, Farmingdale, Riverhead. The table lists every rate center — the billing locality each prefix is anchored to — with its share of the code's 782 active prefixes.

Ranked by active prefixes, the code's territory runs through Brentwood, Farmingdale, Riverhead, Huntington, Central Islip, Amityville, Babylon and Deer Park, and 45 smaller communities down to single-prefix localities.

Metropolitan coverage: 54 rate centers belong to FCC top-100 metro areas.

Overlap note: 47 localities are shared with other area codes, so a neighbor's number may differ in its first three digits.

Clock-wise the coverage is Eastern.

A caller's real location can differ: numbers port between carriers and follow their owners when they move. Use the prefix tables to see where a specific number block was issued.

FAQ

What is the biggest city in area code 631?

Brentwood holds the most active prefixes (127), making it the code's largest numbering locality.

How many places does 631 cover?

54 rate centers in New York hold active 631 prefixes, from Brentwood down to communities with a single prefix.

Does a 631 number guarantee the caller lives in one of these places?

No — the tables show where number blocks were issued. Porting and VoIP let people keep or acquire numbers anywhere.