NumberResearch Membership · Data 09/21/2026

Thousands-blocks in 517-451

This prefix’s ten 1,000-number blocks and who holds each — 10 on record · from the daily NANPA thousands-block report, 09/21/2026

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

The ten 1,000-number thousand-blocks inside prefix 517-451 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
FRONTIER NORTH, INC. - MI 5
TC3 TELECOM, INC. - MI 1
ONVOY, LLCV - MI 1
DEERFIELD FARMERS' TELEPHONE COMPANY - MI 1
COMCAST IP PHONE, 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
2005-02-09 517-451-0XXX 0000–0999Assigned DEERFIELD FARMERS' TELEPHONE COMPANY - MI 558A BRITTON MI
2005-06-24 517-451-1XXX 1000–1999Assigned ACD TELECOM, INC. - MI 3535 BRITTON MI
— 517-451-2XXX 2000–2999Reserved FRONTIER NORTH, INC. - MI 0695 BRITTON MI
2007-02-06 517-451-3XXX 3000–3999Assigned ONVOY, LLCV - MI 543C BRITTON MI
— 517-451-4XXX 4000–4999Reserved FRONTIER NORTH, INC. - MI 0695 BRITTON MI
— 517-451-5XXX 5000–5999Reserved FRONTIER NORTH, INC. - MI 0695 BRITTON MI
2010-10-06 517-451-6XXX 6000–6999Assigned TC3 TELECOM, INC. - MI 3459 BRITTON MI
2007-06-13 517-451-7XXX 7000–7999Assigned COMCAST IP PHONE, LLC 318J BRITTON MI
— 517-451-8XXX 8000–8999Reserved FRONTIER NORTH, INC. - MI 0695 BRITTON MI
— 517-451-9XXX 9000–9999Reserved FRONTIER NORTH, INC. - MI 0695 BRITTON MI

Source: NANPA Thousands Block Assignment Report (All Regions, Public), file date 09/21/2026 — Tier A primary source, refreshed on every import. Viewing is free; bulk downloads require a membership.