All assignees
768 prefixes in 406 · initial assignments from the NANPA CO code file, 09/17/2026
| NPA-NXX | Rate center | OCN | Assigned | Pooled |
|---|---|---|---|---|
| 406-500 | BILLINGS | 965H | 2019-01-29 | Yes |
| 406-501 | WHITEHALL | 453F | 2019-08-20 | Yes |
| 406-502 | HELENA | 792K | 2012-04-03 | Yes |
| 406-503 | BILLINGS | 318J | 2023-04-05 | Yes |
| 406-504 | FAIRFIELD | 9415 | 2021-02-12 | Yes |
| 406-505 | CONRAD | 6010 | 2010-10-14 | Yes |
| 406-506 | BILLINGS | 321J | 2020-06-01 | Yes |
| 406-507 | WHITEFISH | 9415 | 2023-02-17 | Yes |
| 406-508 | FRENCHTOWN | 9415 | 2012-02-03 | Yes |
| 406-509 | MISSOULA | 114J | 2026-06-05 | Yes |
| 406-510 | MISSOULA | 453F | 2017-03-22 | Yes |
| 406-511 | XXXXXXXXXX | MULT | — | — |
| 406-512 | BOULDER | 9415 | 2023-02-22 | Yes |
| 406-513 | HELENA | 792K | 2008-04-08 | Yes |
| 406-514 | CULBERTSON | 6010 | 2010-10-20 | Yes |
| 406-515 | SUPERIOR | 6010 | 2010-10-12 | Yes |
| 406-516 | LAUREL | 490J | 2023-04-27 | Yes |
| 406-517 | LIVINGSTON | 6564 | 2024-06-07 | Yes |
| 406-518 | GALATNGTWY | 453F | 2011-09-27 | Yes |
| 406-519 | MISSOULA | 515J | — | Yes |
| 406-520 | ABSAROKEE | 321J | — | Yes |
| 406-521 | TOWNSEND | 6564 | — | Yes |
| 406-522 | BOZEMAN | 9636 | — | — |
| 406-523 | MISSOULA | 9636 | — | — |
| 406-524 | VLINSTRLPK | 2247 | — | Yes |
| 406-525 | SO WOLF PT | 2246 | — | Yes |
| 406-526 | FORT PECK | 2247 | — | Yes |
| 406-527 | SACO | 2247 | — | Yes |
| 406-528 | RONAN | 2252 | — | — |
| 406-529 | MISSOULA | 6564 | 2005-09-16 | — |
| 406-530 | LAUREL | 9415 | — | Yes |
| 406-531 | MISSOULA | 6564 | — | — |
| 406-532 | MISSOULA | 7870 | — | — |
| 406-533 | BUTTE | 9636 | — | Yes |
| 406-534 | BILLINGS | 792K | — | Yes |
| 406-535 | LEWISTOWN | 7830 | — | — |
| 406-536 | BOZEMAN | 6010 | 2024-12-18 | Yes |
| 406-537 | MELVILLE | 2257 | — | — |
| 406-538 | LEWISTOWN | 9636 | — | Yes |
| 406-539 | BOZEMAN | 6010 | — | — |
| 406-540 | MISSOULA | 453F | — | Yes |
| 406-541 | MISSOULA | 7870 | — | — |
| 406-542 | MISSOULA | 9636 | — | — |
| 406-543 | MISSOULA | 9636 | — | — |
| 406-544 | MISSOULA | 6564 | — | — |
| 406-545 | BILLINGS | 9415 | 2002-06-19 | Yes |
| 406-546 | MISSOULA | 6564 | — | — |
| 406-547 | WHSLPHRSPG | 3310 | — | Yes |
| 406-548 | BOZEMAN | 9636 | — | Yes |
| 406-549 | MISSOULA | 9636 | — | — |
| 406-550 | MISSOULA | 732J | — | Yes |
| 406-551 | BOZEMAN | 9415 | 2002-06-19 | Yes |
| 406-552 | MISSOULA | 9415 | 2002-06-19 | Yes |
| 406-553 | DIVIDE | 6010 | — | Yes |
| 406-554 | NO BROADUS | 2251 | — | — |
| 406-555 | DIR ASST | MULT | — | — |
| 406-556 | BOZEMAN | 9636 | — | — |
| 406-557 | JORDAN | 2246 | — | Yes |
| 406-558 | HELENA | 7229 | 2002-06-19 | Yes |
| 406-559 | ANACONDA | 6564 | — | Yes |
| 406-560 | ANACONDA | 6564 | — | Yes |
| 406-561 | BILLINGS | 6529 | 2017-08-02 | Yes |
| 406-562 | AUGUSTA | 2255 | — | — |
| 406-563 | ANACONDA | 9636 | — | Yes |
| 406-564 | GREATFALLS | 9415 | 2002-06-19 | Yes |
| 406-565 | BUTTE | 9415 | 2002-06-19 | Yes |
| 406-566 | STANFORD | 3310 | — | Yes |
| 406-567 | DENTON | 3310 | — | — |
| 406-568 | RYEGATE | 2246 | — | Yes |
| 406-569 | WSQUAW GAP | 1632 | — | — |
| 406-570 | BOZEMAN | 6564 | — | — |
| 406-571 | FINLEY PT | 792K | — | Yes |
| 406-572 | MARTINSDL | 3310 | — | — |
| 406-573 | BROWNING | 619J | — | Yes |
| 406-574 | SILVERTIP | 9636 | — | Yes |
| 406-575 | NO RYEGATE | 2246 | — | — |
| 406-576 | CONRAD | 6010 | — | Yes |
| 406-577 | BOZEMAN | 453F | — | Yes |
| 406-578 | WILSALL | 9636 | — | Yes |
| 406-579 | BOZEMAN | 6564 | — | — |
| 406-580 | BOZEMAN | 6010 | — | — |
| 406-581 | BOZEMAN | 6564 | — | — |
| 406-582 | BOZEMAN | 9636 | — | — |
| 406-583 | BLOOMFIELD | 2246 | — | — |
| 406-584 | LINDSAY | 2246 | — | Yes |
| 406-585 | BOZEMAN | 9636 | — | — |
| 406-586 | BOZEMAN | 9636 | — | — |
| 406-587 | BOZEMAN | 9636 | — | — |
| 406-588 | CARLYLE | 2246 | — | — |
| 406-589 | BOZEMAN | 6529 | — | Yes |
| 406-590 | GREATFALLS | 6564 | — | — |
| 406-591 | BILLINGS | 6564 | — | — |
| 406-592 | BUSBY | 2251 | — | Yes |
| 406-593 | BUTTE | 6010 | — | Yes |
| 406-594 | HELENA | 6564 | — | — |
| 406-595 | BOZEMAN | 6564 | — | — |
| 406-596 | DILLON | 6010 | — | Yes |
| 406-597 | SHELBY | 6010 | — | Yes |
| 406-598 | BILLINGS | 6564 | — | — |
| 406-599 | BOZEMAN | 6564 | 2004-10-26 | — |
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.