NumberResearchThousands-blocks in 517-851
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 517-851 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 517 blocks
Most active assignees, all time — NPA 517
New assignments by month
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| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| — | 517-851-0XXX | 0000–0999 | Reserved | FRONTIER MIDSTATES, INC. - MI | 0681 | STOCKBDG | MI |
| 2009-08-27 | 517-851-1XXX | 1000–1999 | Assigned | NEW CINGULAR WIRELESS PCS, LLC - IL | 6534 | STOCKBDG | MI |
| 2003-10-29 | 517-851-2XXX | 2000–2999 | Assigned | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MI | 6003 | STOCKBDG | MI |
| 2004-06-22 | 517-851-3XXX | 3000–3999 | Assigned | LEVEL 3 COMMUNICATIONS, LLC - MI | 6120 | STOCKBDG | MI |
| — | 517-851-4XXX | 4000–4999 | Reserved | FRONTIER MIDSTATES, INC. - MI | 0681 | STOCKBDG | MI |
| — | 517-851-5XXX | 5000–5999 | Reserved | FRONTIER MIDSTATES, INC. - MI | 0681 | STOCKBDG | MI |
| — | 517-851-6XXX | 6000–6999 | Reserved | FRONTIER MIDSTATES, INC. - MI | 0681 | STOCKBDG | MI |
| — | 517-851-7XXX | 7000–7999 | Reserved | FRONTIER MIDSTATES, INC. - MI | 0681 | STOCKBDG | MI |
| — | 517-851-8XXX | 8000–8999 | Reserved | FRONTIER MIDSTATES, INC. - MI | 0681 | STOCKBDG | MI |
| — | 517-851-9XXX | 9000–9999 | Reserved | FRONTIER MIDSTATES, INC. - MI | 0681 | STOCKBDG | MI |
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.