NumberResearchThousands-blocks in 231-238
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 231-238 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
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Oct 2025
| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| — | 231-238-0XXX | 0000–0999 | Reserved | MICHIGAN BELL TEL CO | 9323 | INDIAN RIV | MI |
| — | 231-238-1XXX | 1000–1999 | Reserved | MICHIGAN BELL TEL CO | 9323 | INDIAN RIV | MI |
| 2008-02-27 | 231-238-2XXX | 2000–2999 | Assigned | CHARTER IP ENABLED SERVICES, LLC | 792K | INDIAN RIV | MI |
| 2011-02-10 | 231-238-3XXX | 3000–3999 | Assigned | BANDWIDTH.COM CLEC, LLC - MI | 991E | INDIAN RIV | MI |
| — | 231-238-4XXX | 4000–4999 | Reserved | MICHIGAN BELL TEL CO | 9323 | INDIAN RIV | MI |
| 2011-08-11 | 231-238-5XXX | 5000–5999 | Assigned | AT&T ENTERPRISES, LLC | 516C | INDIAN RIV | MI |
| — | 231-238-6XXX | 6000–6999 | Reserved | MICHIGAN BELL TEL CO | 9323 | INDIAN RIV | MI |
| — | 231-238-7XXX | 7000–7999 | Reserved | MICHIGAN BELL TEL CO | 9323 | INDIAN RIV | MI |
| — | 231-238-8XXX | 8000–8999 | Reserved | MICHIGAN BELL TEL CO | 9323 | INDIAN RIV | MI |
| — | 231-238-9XXX | 9000–9999 | Reserved | MICHIGAN BELL TEL CO | 9323 | INDIAN RIV | 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.