NumberResearch Membership · Data 09/20/2026

Thousands-blocks in 231-256

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

Full prefixes (NXX) Thousands-blocks (1,000-number pools)

The ten 1,000-number thousand-blocks inside prefix 231-256 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
MICHIGAN BELL TEL CO 5
TELEPORT COMMUNICATIONS AMERICA, LLC - MI 1
PAETEC ITEL, LLC 1
LEVEL 3 COMMUNICATIONS, LLC - MI 1
CLEAR RATE COMMUNICATIONS, LLC 1
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
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Recent thousands-block assignments
AssignedThousands-blockLast 4 digitsStatusAssigneeOCNRate centerState
— 231-256-0XXX 0000–0999Reserved MICHIGAN BELL TEL CO 9323 LKLEELANAU MI
2004-10-14 231-256-1XXX 1000–1999Assigned LEVEL 3 COMMUNICATIONS, LLC - MI 6120 LKLEELANAU MI
— 231-256-2XXX 2000–2999Reserved MICHIGAN BELL TEL CO 9323 LKLEELANAU MI
2003-12-30 231-256-3XXX 3000–3999Assigned PAETEC ITEL, LLC 829J LKLEELANAU MI
2013-02-22 231-256-4XXX 4000–4999Assigned CLEAR RATE COMMUNICATIONS, LLC 046L LKLEELANAU MI
2013-07-11 231-256-5XXX 5000–5999Assigned TELEPORT COMMUNICATIONS AMERICA, LLC - MI 770E LKLEELANAU MI
2015-08-12 231-256-6XXX 6000–6999Assigned CENTURYLINK COMMUNICATIONS, LLC 508J LKLEELANAU MI
— 231-256-7XXX 7000–7999Reserved MICHIGAN BELL TEL CO 9323 LKLEELANAU MI
— 231-256-8XXX 8000–8999Reserved MICHIGAN BELL TEL CO 9323 LKLEELANAU MI
— 231-256-9XXX 9000–9999Reserved MICHIGAN BELL TEL CO 9323 LKLEELANAU 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.