NumberResearchThousands-blocks in 423-433
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 423-433 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 423 blocks
Most active assignees, all time — NPA 423
New assignments by month
Sep 2026
Aug 2026
Jul 2026
Jun 2026
May 2026
Apr 2026
Mar 2026
Feb 2026
Jan 2026
Dec 2025
Nov 2025
Oct 2025
| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| — | 423-433-0XXX | 0000–0999 | Reserved | UNITED TELEPHONE-SOUTHEAST-TN DBA CENTURYLINK - TN | 4510 | JOHNSON CY | TN |
| — | 423-433-1XXX | 1000–1999 | Reserved | UNITED TELEPHONE-SOUTHEAST-TN DBA CENTURYLINK - TN | 4510 | JOHNSON CY | TN |
| — | 423-433-2XXX | 2000–2999 | Reserved | UNITED TELEPHONE-SOUTHEAST-TN DBA CENTURYLINK - TN | 4510 | JOHNSON CY | TN |
| — | 423-433-3XXX | 3000–3999 | Reserved | UNITED TELEPHONE-SOUTHEAST-TN DBA CENTURYLINK - TN | 4510 | JOHNSON CY | TN |
| — | 423-433-4XXX | 4000–4999 | Reserved | UNITED TELEPHONE-SOUTHEAST-TN DBA CENTURYLINK - TN | 4510 | JOHNSON CY | TN |
| — | 423-433-5XXX | 5000–5999 | Reserved | UNITED TELEPHONE-SOUTHEAST-TN DBA CENTURYLINK - TN | 4510 | JOHNSON CY | TN |
| — | 423-433-6XXX | 6000–6999 | Reserved | UNITED TELEPHONE-SOUTHEAST-TN DBA CENTURYLINK - TN | 4510 | JOHNSON CY | TN |
| 2008-03-28 | 423-433-7XXX | 7000–7999 | Assigned | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN | 6673 | JOHNSON CY | TN |
| 2007-11-14 | 423-433-8XXX | 8000–8999 | Assigned | SUNCOM DBA T-MOBILE USA | 8645 | JOHNSON CY | TN |
| 2008-08-25 | 423-433-9XXX | 9000–9999 | Assigned | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN | 6673 | JOHNSON CY | TN |
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.