NumberResearchThousands-blocks in 406-357
This prefix’s ten 1,000-number blocks and who holds each — 10 on record · from the daily NANPA thousands-block report, 09/20/2026
The ten 1,000-number thousand-blocks inside prefix 406-357 and who was initially assigned each. Under pooling these blocks often belong to different carriers — the single prefix-level “assignee” is usually just the pool / code holder, not who holds the numbers. ← all 406 blocks
Most active assignees, all time — NPA 406
New assignments by month
Sep 2026
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Oct 2025
| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| — | 406-357-0XXX | 0000–0999 | Reserved | TRIANGLE TEL. COOP. ASSN., INC. | 2257 | CHINOOK | MT |
| 2019-11-04 | 406-357-1XXX | 1000–1999 | Assigned | LEVEL 3 COMMUNICATIONS, LLC - MT | 9415 | CHINOOK | MT |
| — | 406-357-2XXX | 2000–2999 | Reserved | TRIANGLE TEL. COOP. ASSN., INC. | 2257 | CHINOOK | MT |
| — | 406-357-3XXX | 3000–3999 | Reserved | TRIANGLE TEL. COOP. ASSN., INC. | 2257 | CHINOOK | MT |
| — | 406-357-4XXX | 4000–4999 | Reserved | TRIANGLE TEL. COOP. ASSN., INC. | 2257 | CHINOOK | MT |
| 2022-12-27 | 406-357-5XXX | 5000–5999 | Assigned | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MT | 6564 | CHINOOK | MT |
| 2021-04-09 | 406-357-6XXX | 6000–6999 | Assigned | CHARTER IP ENABLED SERVICES, LLC | 792K | CHINOOK | MT |
| 2020-01-31 | 406-357-7XXX | 7000–7999 | Assigned | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MT | 6564 | CHINOOK | MT |
| — | 406-357-8XXX | 8000–8999 | Reserved | TRIANGLE TEL. COOP. ASSN., INC. | 2257 | CHINOOK | MT |
| 2026-02-04 | 406-357-9XXX | 9000–9999 | Assigned | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MT | 6564 | CHINOOK | MT |
Source: NANPA Thousands Block Assignment Report (All Regions, Public), file date 09/20/2026 — Tier A primary source, refreshed on every import. Viewing is free; bulk downloads require a membership.