NumberResearchThousands-blocks in 423-537
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 423-537 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
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Oct 2025
| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| — | 423-537-0XXX | 0000–0999 | Available | BULLS GAP | TN | ||
| — | 423-537-1XXX | 1000–1999 | Reserved | PAETEC ITEL, LLC | 829J | BULLS GAP | TN |
| — | 423-537-2XXX | 2000–2999 | Reserved | PAETEC ITEL, LLC | 829J | BULLS GAP | TN |
| — | 423-537-3XXX | 3000–3999 | Reserved | PAETEC ITEL, LLC | 829J | BULLS GAP | TN |
| 2018-03-01 | 423-537-4XXX | 4000–4999 | Assigned | ONVOY, LLC - TN | 525E | BULLS GAP | TN |
| — | 423-537-5XXX | 5000–5999 | Reserved | PAETEC ITEL, LLC | 829J | BULLS GAP | TN |
| 2016-02-26 | 423-537-6XXX | 6000–6999 | Assigned | ONVOY, LLC - TN | 525E | BULLS GAP | TN |
| — | 423-537-7XXX | 7000–7999 | Available | BULLS GAP | TN | ||
| 2016-02-26 | 423-537-8XXX | 8000–8999 | Assigned | ONVOY, LLC - TN | 525E | BULLS GAP | TN |
| — | 423-537-9XXX | 9000–9999 | Available | BULLS GAP | 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.