NumberResearchThousands-blocks in 231-640
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 231-640 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 231 blocks
Most active assignees, all time — NPA 231
New assignments by month
Sep 2026
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Oct 2025
| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| — | 231-640-0XXX | 0000–0999 | Reserved | NEW CINGULAR WIRELESS PCS, LLC - IL | 6534 | LAKE ANN | MI |
| 2005-01-12 | 231-640-1XXX | 1000–1999 | Assigned | ACD TELECOM, INC. - MI | 3535 | LAKE ANN | MI |
| 2012-09-25 | 231-640-2XXX | 2000–2999 | Assigned | CHARTER IP ENABLED SERVICES, LLC | 792K | LAKE ANN | MI |
| 2021-05-20 | 231-640-3XXX | 3000–3999 | Assigned | ONVOY SPECTRUM, LLC | 624H | LAKE ANN | MI |
| 2009-06-05 | 231-640-4XXX | 4000–4999 | Assigned | NEW CINGULAR WIRELESS PCS, LLC - IL | 6534 | LAKE ANN | MI |
| 2019-08-06 | 231-640-5XXX | 5000–5999 | Assigned | ONVOY, LLCV - MI | 543C | LAKE ANN | MI |
| 2017-05-17 | 231-640-6XXX | 6000–6999 | Assigned | LEVEL 3 COMMUNICATIONS, LLC - MI | 6120 | LAKE ANN | MI |
| 2020-10-22 | 231-640-7XXX | 7000–7999 | Assigned | ONVOY, LLCV - MI | 543C | LAKE ANN | MI |
| 2020-10-22 | 231-640-8XXX | 8000–8999 | Assigned | ONVOY, LLCV - MI | 543C | LAKE ANN | MI |
| 2016-03-02 | 231-640-9XXX | 9000–9999 | Assigned | NEW CINGULAR WIRELESS PCS, LLC - IL | 6534 | LAKE ANN | MI |
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.