Area code 231

Area code 231 at a glance

231 is one of 13 geographic area codes serving Michigan; NANPA records its in-service date as June 5, 1999. It is not part of an overlay, so every number in its territory starts with 231. It is in the Eastern time zone. The places with the most assigned exchanges include Muskegon, Traverse City, Petoskey, Cadillac, and Big Rapids. By population, its largest named places are Shelby, Muskegon, Traverse City, Fruitport, and Marion.

Places served by 231

231 holds 8.3% of the 6,882 central office codes assigned in Michigan, the 6th most of the state's 13 codes. 70 Census places could be matched to rate centers with 231 exchanges; the most populous are Shelby (80,425), Muskegon (37,287), Traverse City (15,782), and Fruitport (15,458). For a storefront or service area inside 231, the place pages show which prefixes are rated local there.

Ten-digit and seven-digit dialing in 231

According to NANPA's dialing-plan data, local calls within 231 are dialed as seven digits and toll calls as 1 plus ten digits. Seven-digit local dialing is still permitted here, but customers calling from other area codes, and every mobile contact list, use all ten digits.

Carriers with 231 numbers

42 carriers hold the 572 central office codes assigned in 231. New Cingular Wireless PCS, LLC - Il has the most, with 72 (13%). 382 of the codes (67%) are pooled, meaning the code holder shares blocks of 1,000 numbers with other carriers instead of using all 10,000 itself. Numbers can move between carriers through porting, so a code's holder tells you where the block started, not where every number lives now.

Where 231 numbers are rated

NANPA assigns each central office code to a rate center, the local calling area that decides whether a call is local or toll. 231 has codes in 99 rate centers. The table lists the rate centers with the most codes, with the matching Census place where the abbreviation could be matched.

231 code assignments over time

An area code has 800 possible central office codes that start with 2 through 9, a few of which are reserved (such as N11 service codes and 555). 572 are assigned in 231, 72% of 800. 77 were assigned in 2020 or later.

Getting a 231 number for your business

For $99 a month, Callata puts a team of up to 5 on one plan ($20 for each person after that): up to 3 local numbers, unlimited inbound calls, a pooled allowance of 1,500 outbound US and Canada minutes per user, browser and cell calling, voicemail transcription with urgency triage, recorded calls with AI summaries and business-hours routing, with E911 on every number.

If you already have a number in area code 231, porting it to Callata is free. Texting from a local number requires a one-time carrier registration (10DLC, $49), and the numbers available in any area code depend on carrier inventory when you choose them.

Optional AI agents (receptionist, sales, support or scheduler) can answer calls after hours or when nobody picks up, take messages, text, email and transfer to your team. They are billed from prepaid AI minutes at $0.25 per minute, identify themselves as AI, and may only place outbound calls to people who consented, between 8am and 9pm.