NumberResearchThousands-blocks in 251-531
This prefix’s ten 1,000-number blocks and who holds each — 10 on record · from the daily NANPA thousands-block report, 09/19/2026
The ten 1,000-number thousand-blocks inside prefix 251-531 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 251 blocks
Most active assignees, all time — NPA 251
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 |
|---|---|---|---|---|---|---|---|
| 2026-05-29 | 251-531-0XXX | 0000–0999 | Assigned | IP HORIZON LLC | 515J | MT VERNON | AL |
| — | 251-531-1XXX | 1000–1999 | Available | MT VERNON | AL | ||
| 2025-08-21 | 251-531-2XXX | 2000–2999 | Assigned | HD CARRIER LLC | 321J | MT VERNON | AL |
| 2025-08-21 | 251-531-3XXX | 3000–3999 | Assigned | HD CARRIER LLC | 321J | MT VERNON | AL |
| 2025-08-21 | 251-531-4XXX | 4000–4999 | Assigned | HD CARRIER LLC | 321J | MT VERNON | AL |
| — | 251-531-5XXX | 5000–5999 | Available | MT VERNON | AL | ||
| — | 251-531-6XXX | 6000–6999 | Available | MT VERNON | AL | ||
| — | 251-531-7XXX | 7000–7999 | Available | MT VERNON | AL | ||
| — | 251-531-8XXX | 8000–8999 | Available | MT VERNON | AL | ||
| — | 251-531-9XXX | 9000–9999 | Available | MT VERNON | AL |
Source: NANPA Thousands Block Assignment Report (All Regions, Public), file date 09/19/2026 — Tier A primary source, refreshed on every import. Viewing is free; bulk downloads require a membership.