All assignees
768 prefixes in 406 · initial assignments from the NANPA CO code file, 09/17/2026
| NPA-NXX | Rate center | OCN | Assigned | Pooled |
|---|---|---|---|---|
| 406-600 | BOZEMAN | 6564 | 2006-04-13 | — |
| 406-601 | BILLINGS | 7870 | 2013-11-08 | Yes |
| 406-602 | BOZEMAN | 7870 | 2013-11-08 | Yes |
| 406-603 | HELENA | 7870 | 2013-11-08 | Yes |
| 406-604 | GREATFALLS | 7870 | 2011-07-15 | Yes |
| 406-605 | BUTTE | 073H | 2021-04-18 | Yes |
| 406-606 | BILLINGS | 935G | 2012-12-07 | Yes |
| 406-607 | KALISPELL | 7870 | 2013-11-08 | Yes |
| 406-608 | BILLINGS | 515J | 2021-05-06 | Yes |
| 406-609 | KALISPELL | 6010 | 2021-03-24 | Yes |
| 406-610 | MISSOULA | 6010 | 2025-01-06 | Yes |
| 406-611 | XXXXXXXXXX | MULT | — | — |
| 406-612 | SWAN LAKE | 453F | 2007-10-11 | Yes |
| 406-613 | BOZEMAN | 508J | 2022-06-16 | Yes |
| 406-614 | BIGFORK | 453F | 2020-10-13 | Yes |
| 406-615 | THOMPSNFLS | 986F | 2014-04-28 | Yes |
| 406-616 | THREEFORKS | 453F | 2011-07-01 | Yes |
| 406-617 | BILLINGS | 6010 | 2024-12-23 | Yes |
| 406-618 | MISSOULA | 520K | 2025-10-09 | Yes |
| 406-620 | BILLINGS | 443B | 2005-12-06 | — |
| 406-621 | FORTBENTON | 6564 | — | Yes |
| 406-622 | FORTBENTON | 3310 | — | Yes |
| 406-623 | HARDIN | 939H | — | Yes |
| 406-624 | BOZEMAN | 746D | 2005-02-03 | Yes |
| 406-625 | STEVENSVL | 7421 | — | Yes |
| 406-626 | FRENCHTOWN | 9636 | — | Yes |
| 406-627 | EASTCONRAD | 2255 | — | — |
| 406-628 | LAUREL | 9636 | — | Yes |
| 406-629 | HARDIN | 453F | — | Yes |
| 406-630 | SIDNEY | 9415 | 2005-02-16 | Yes |
| 406-631 | ELMO | 453F | 2007-07-26 | Yes |
| 406-632 | HARLOWTON | 3310 | — | Yes |
| 406-633 | LAUREL | 9636 | — | Yes |
| 406-634 | HELENA | 453F | — | Yes |
| 406-635 | TERRY | 2246 | — | Yes |
| 406-636 | LAVINA | 2246 | — | — |
| 406-637 | TERRY | 9636 | — | Yes |
| 406-638 | HARDIN | 2250 | — | Yes |
| 406-639 | LODGEGRASS | 2250 | — | — |
| 406-640 | WYELLOWSTN | 6564 | — | Yes |
| 406-641 | WYELLOWSTN | 6564 | — | Yes |
| 406-642 | VICTOR | 9636 | — | Yes |
| 406-643 | NO PARKMAN | 453F | 2007-05-24 | Yes |
| 406-644 | CHARLO | 2235 | — | Yes |
| 406-645 | DEER LODGE | 453F | — | Yes |
| 406-646 | WYELLOWSTN | 9636 | — | Yes |
| 406-647 | BILLINGS | 994E | 2008-07-03 | Yes |
| 406-648 | NOHINSDALE | 2247 | — | Yes |
| 406-649 | ST REGIS | 2235 | — | Yes |
| 406-650 | WOLF POINT | 443B | — | — |
| 406-651 | BILLINGS | 9636 | — | Yes |
| 406-652 | BILLINGS | 9636 | — | — |
| 406-653 | WOLF POINT | 2247 | — | Yes |
| 406-654 | MALTA | 3310 | — | Yes |
| 406-655 | BILLINGS | 9636 | — | — |
| 406-656 | BILLINGS | 9636 | — | — |
| 406-657 | BILLINGS | 9636 | — | — |
| 406-658 | SOUTHMALTA | 2257 | — | — |
| 406-659 | NO PARKMAN | 9636 | — | Yes |
| 406-660 | DILLON | 6010 | — | Yes |
| 406-661 | BILLINGS | 6564 | — | Yes |
| 406-662 | BRIDGER | 9636 | — | Yes |
| 406-663 | RAPELJE | 2257 | — | — |
| 406-664 | BELFRY | 2250 | — | — |
| 406-665 | HARDIN | 9636 | — | Yes |
| 406-666 | FORT SMITH | 2250 | — | — |
| 406-667 | BROADVIEW | 2257 | — | — |
| 406-668 | FROMBERG | 9636 | — | Yes |
| 406-669 | MOLT | 2257 | — | — |
| 406-670 | BILLINGS | 6564 | — | — |
| 406-671 | BILLINGS | 6564 | — | — |
| 406-672 | BILLINGS | 6564 | — | — |
| 406-673 | HAYS | 2257 | — | Yes |
| 406-674 | WHITEWATER | 2257 | — | Yes |
| 406-675 | PABLO | 2252 | — | — |
| 406-676 | RONAN | 2252 | — | — |
| 406-677 | SEELEYLAKE | 2235 | — | Yes |
| 406-678 | HAUGAN | 2235 | — | — |
| 406-679 | HARDIN | 732J | — | Yes |
| 406-680 | MALTA | 443B | 2005-01-10 | Yes |
| 406-681 | GRANT | 2254 | — | — |
| 406-682 | ENNIS | 2255 | — | Yes |
| 406-683 | DILLON | 9636 | — | — |
| 406-684 | TWINBRIDGS | 2255 | — | — |
| 406-685 | HARRISON | 2255 | — | — |
| 406-686 | CLYDE PARK | 9636 | — | Yes |
| 406-687 | W GLENDIVE | 2246 | — | Yes |
| 406-688 | SCOBEY | 443B | 2014-02-10 | Yes |
| 406-689 | WISDOM | 2254 | — | — |
| 406-690 | BILLINGS | 6564 | — | — |
| 406-691 | ANACONDA | 6010 | — | Yes |
| 406-692 | YELLOW BAY | 453F | 2007-10-11 | Yes |
| 406-693 | WARM SPG | 9636 | — | Yes |
| 406-694 | BILLINGS | 6564 | 2005-01-05 | Yes |
| 406-695 | FRAZER | 2247 | — | Yes |
| 406-696 | BILLINGS | 6564 | 2006-06-15 | — |
| 406-697 | BILLINGS | 6564 | 2005-04-21 | — |
| 406-698 | BILLINGS | 6564 | — | — |
| 406-699 | HARDIN | 6010 | — | Yes |
| 406-700 | — | — |
These are initial assignees from NANPA CO-code records — because of number portability, the current serving carrier of individual numbers may differ. Bulk export requires a membership.