Phone numbers in Roundup, Montana
Roundup has 4 phone prefixes in area code 406.
Biggest holders: Verizon Wireless, Mid-rivers Tel. Coop. This is the local calling area (rate center) where those prefixes were first assigned.
- Mobile carrier 75%
- Phone company 25%
Every prefix in Roundup
Search the first six digits of a number in this list. If it's here, the number started in Roundup with the carrier shown. If it isn't, check the Montana page or look the number up.
| Prefix | Carrier | Type | Assigned |
|---|---|---|---|
| 406-320 | Verizon Wireless | Mobile carrier | – |
| 406-323 | Mid-rivers Tel. Coop | Phone company | – |
| 406-331 | Verizon Wireless | Mobile carrier | – |
| 406-913 | Verizon Wireless | Mobile carrier | – |
Most prefixes are pooled: the 10,000 numbers in each are handed out in blocks of 1,000 to different carriers, and people can also take their numbers to another carrier. So the carrier shown is where the prefix started, not a guarantee about any one number. Source: NANPA central office code records, 2026-10-10.