NumberResearchThousands-blocks in 406-574
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 406-574 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
Aug 2026
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Dec 2025
Nov 2025
Oct 2025
| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| 2018-07-13 | 406-574-0XXX | 0000–0999 | Assigned | TELNYX LLC | 073H | SILVERTIP | MT |
| — | 406-574-1XXX | 1000–1999 | Reserved | QWEST CORPORATION | 9636 | SILVERTIP | MT |
| 2021-06-07 | 406-574-2XXX | 2000–2999 | Assigned | ONVOY, LLC - MT | 453F | SILVERTIP | MT |
| — | 406-574-3XXX | 3000–3999 | Reserved | QWEST CORPORATION | 9636 | SILVERTIP | MT |
| 2023-02-06 | 406-574-4XXX | 4000–4999 | Assigned | LEVEL 3 COMMUNICATIONS, LLC - MT | 9415 | SILVERTIP | MT |
| 2023-11-15 | 406-574-5XXX | 5000–5999 | Assigned | NUSO, LLC | 478J | SILVERTIP | MT |
| 2023-11-15 | 406-574-6XXX | 6000–6999 | Assigned | NUSO, LLC | 478J | SILVERTIP | MT |
| 2015-02-12 | 406-574-7XXX | 7000–7999 | Assigned | CENTURYLINK COMMUNICATIONS, LLC | 508J | SILVERTIP | MT |
| 2020-09-11 | 406-574-8XXX | 8000–8999 | Assigned | NUSO, LLC | 478J | SILVERTIP | MT |
| — | 406-574-9XXX | 9000–9999 | Available | SILVERTIP | 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.