NumberResearchThousands-blocks in 310-921
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 310-921 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 310 blocks
Most active assignees, all time — NPA 310
New assignments by month
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Oct 2025
| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| 2011-03-21 | 310-921-0XXX | 0000–0999 | Assigned | METROPCS NETWORKS, LLC | 899D | REDONDO | CA |
| — | 310-921-1XXX | 1000–1999 | Reserved | FRONTIER CALIFORNIA INC. | 2319 | REDONDO | CA |
| — | 310-921-2XXX | 2000–2999 | Reserved | FRONTIER CALIFORNIA INC. | 2319 | REDONDO | CA |
| — | 310-921-3XXX | 3000–3999 | Reserved | FRONTIER CALIFORNIA INC. | 2319 | REDONDO | CA |
| — | 310-921-4XXX | 4000–4999 | Reserved | FRONTIER CALIFORNIA INC. | 2319 | REDONDO | CA |
| 2006-04-14 | 310-921-5XXX | 5000–5999 | Assigned | LEVEL 3 COMMUNICATIONS, LLC - CA | 8826 | REDONDO | CA |
| — | 310-921-6XXX | 6000–6999 | Reserved | FRONTIER CALIFORNIA INC. | 2319 | REDONDO | CA |
| 2005-10-03 | 310-921-7XXX | 7000–7999 | Assigned | PAETEC ITEL, LLC | 829J | REDONDO | CA |
| 2013-06-10 | 310-921-8XXX | 8000–8999 | Assigned | TWC IP ENABLED SERVICES, LLC | 793K | REDONDO | CA |
| — | 310-921-9XXX | 9000–9999 | Reserved | FRONTIER CALIFORNIA INC. | 2319 | REDONDO | CA |
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.