Area code
406
406 is a United States area code. Under the North American Numbering Plan it belongs to Montana, which has 1 area code in total.
Validate a number in 406
Paste a full number and the tool checks it against the numbering plan. It returns the standard formats, the line type the plan assigns and the area code region.
Digits with or without punctuation work. Numbers outside the US are read with the +country code.
Area code 406 at a glance
NANPA lists 754 central office codes (prefixes) in use in area code 406, held by 63 holders across 260 rate centers.
| Fact | Value |
|---|---|
| In service since | 1947-01-01 |
| Time zone | Mountain (M) |
| Prefixes in use | 754 |
| Pooled prefixes | 527 (70%) |
| Rate centers | 260 |
| Companies holding prefixes | 63 |
| Assignment dates on file | 2001-04-18 to 2026-06-05 (185 prefixes) |
| ZIP codes in its places | 241 |
Rate centers in area code 406
| Rate center | Prefixes | Share |
|---|---|---|
| BILLINGS | 72 | 10% |
| MISSOULA | 47 | 6% |
| HELENA | 38 | 5% |
| GREATFALLS | 37 | 5% |
| BOZEMAN | 32 | 4% |
| KALISPELL | 25 | 3% |
| BUTTE | 17 | 2% |
| MILES CITY | 10 | 1% |
| 252 other rate centers | 476 | 63% |
Who holds the prefixes in 406
Qwest holds the most prefixes, 132 (18%). 70% of the prefixes are pooled, which means their thousands-blocks can belong to different companies.
| Holder | Prefixes | Share |
|---|---|---|
| Qwest | 132 | 18% |
| Verizon Wireless | 119 | 16% |
| New Cingular Wireless PCS | 74 | 10% |
| Onvoy | 43 | 6% |
| Triangle Tel. Coop. Assn. | 39 | 5% |
| Nemont Tel Coop | 33 | 4% |
| 57 other carriers | 314 | 42% |
A prefix holder is the company a code was assigned to, not necessarily a number's current carrier, because numbers can be ported to another company. Find which carrier a number is on, or browse the prefix holders.
History of area code 406
- 1947-01-01 Area code 406 went into service.
Area codes nearest to 406
Distance is measured between the centers of the ZIP code places each area code serves, so it is a rough guide.
ZIP codes in area code 406
241 ZIP codes fall in places that have a rate center in this area code.
| Place | ZIP codes |
|---|---|
| Billings, MT | 14 |
| Helena, MT | 8 |
| Missoula, MT | 8 |
A ZIP code and an area code are unrelated systems. A ZIP code can sit in more than one area code, and an area code spans many ZIP codes.
Complaints on file for 406 numbers
2,105 FCC complaints are on file for 1,735 numbers in 406, most often filed as "Unwanted Calls". These are unverified consumer reports.
| Year of latest complaint | Numbers |
|---|---|
| 2023 | 99 |
| 2024 | 125 |
| 2025 | 126 |
Montana has one area code
406 is the only area code the table assigns to Montana, so every geographic number there starts with it.
Next to 406 in the numbering table
These are the codes just before and after 406 when all are sorted by number. They are neighbours on the list, not necessarily on the map.
What the area code does and does not tell you
A number that starts with 406 was first assigned in Montana. That is a fact about where the number began, and it is a useful hint when you check a form entry, for example a billing address in Montana next to a 406 phone number.
It does not show where the person is today. A number stays with its owner after a move or a change of provider (number portability), and mobile numbers travel with the handset. The area code also cannot tell you whether the line is active, who the carrier is, or whether the number is mobile or fixed: the plan shares those ranges. Read more about the area code, the numbering plan and line type.
Check numbers in bulk with the API
| Product | Credits | Docs |
|---|---|---|
| Phone Numbering-Plan Validation | 1 credit per valid number | API docs |
| Phone Intelligence (carrier and line status) | 1 credit per check (invalid numbers outside the US and Canada are free) | Product page |
Questions about area code 406
Where is area code 406?
NANPA assigns area code 406 to Montana, United States.
In which state does area code 406 sit?
Montana. 406 is one of 1 area code the NANPA table assigns to the state.
Which places does area code 406 cover?
The places with the most ZIP codes among the rate centers in 406 are Billings, MT, Helena, MT and Missoula, MT. The rate center list on this page shows all of them.
Who owns area code 406?
NANPA assigns area codes. Within 406, Qwest holds the most prefixes, 132 prefixes or 18%.
Which time zone does 406 use?
The NANPA NPA report lists the time zone for 406 as Mountain (M).
What year did 406 enter service?
The NANPA NPA report gives an in-service date of 1947-01-01, so 406 has been in use since 1947.
Does area code 406 have an overlay?
The NANPA NPA report lists no other area code in an overlay with 406.
Which area codes are nearest to 406?
The area codes closest to 406, measured between the centers of the ZIP code places they serve, are 208 (about 302 miles), 986 (about 307 miles), 307 (about 325 miles), 509 (about 405 miles) and 385 (about 433 miles).
How many prefixes does area code 406 have?
NANPA's report dated 2026-10-17 lists 754 prefixes in service in 406, spread over 260 rate centers and 63 holders.
Are there complaints about 406 numbers?
The FCC data on file has 2,105 complaints for 1,735 numbers in 406. They are unverified consumer reports. A number with no complaints on file is not proven safe.
Area code assignments: North American Numbering Plan Administrator NPA report, file dated 10/17/2026, retrieved 2026-10-17. Source file. New codes are assigned several times a year. Prefixes, rate centers, holders, time zone, in-service date and overlays: NANPA central office code report dated 2026-10-17 and NPA report dated 2026-10-18. Complaints: FCC consumer complaints open data, fetched 2026-10-17. ZIP code places: Postal code places and coordinates: GeoNames (geonames.org), licensed CC BY 4.0.