NumberResearch Membership · Data 09/25/2026

Recent prefix assignments

0 prefixes assigned in the last 30 days · from the daily NANPA CO code file, 09/25/2026

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

The Code holder is who opened each NPA-NXX prefix — not necessarily who holds the numbers. A prefix is 10,000 numbers, but under pooling its ten 1,000-number blocks are handed out individually, often to different carriers; the code holder may hold only one block, or none. The Thousands-blocks column shows how the ten blocks are really split — click which blocks → to see who holds each 1,000-number block and its last-4-digit range. Assignments are initial assignments; the current serving carrier may differ due to portability.

Most active assignees, all time — NPA 517
FRONTIER NORTH, INC. - MI 30
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 NPA-NXX prefix assignments
AssignedNPA-NXXThousands-blocks taken (last-4 opening)Code holderOCNRate centerState
2015-04-23 517-239 0XXX1XXX3XXX4XXX5XXX6XXX8XXX · 5 holders which blocks → FRONTIER NORTH, INC. - MI 0695 DE WITT MI
2015-04-23 517-312 0–9 XXXall 10 · 5 holders which blocks → FRONTIER NORTH, INC. - MI 0695 ADRIAN MI
— 517-238 6XXX which blocks → FRONTIER NORTH, INC. - MI 0695 COLDWTR LK MI
— 517-263 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 ADRIAN MI
— 517-264 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 ADRIAN MI
— 517-265 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 ADRIAN MI
— 517-266 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 ADRIAN MI
— 517-278 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 COLDWATER MI
— 517-279 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 COLDWATER MI
— 517-283 5XXX6XXX7XXX8XXX9XXX · 4 holders which blocks → FRONTIER NORTH, INC. - MI 0695 READING MI
— 517-369 none assigned yet which blocks → FRONTIER NORTH, INC. - MI 0695 BRONSON MI
— 517-423 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 TECUMSEH MI
— 517-424 2XXX which blocks → FRONTIER NORTH, INC. - MI 0695 TECUMSEH MI
— 517-431 0XXX1XXX4XXX5XXX6XXX7XXX9XXX · 7 holders which blocks → FRONTIER NORTH, INC. - MI 0695 TIPTON MI
— 517-448 0XXX1XXX9XXX · 3 holders which blocks → FRONTIER NORTH, INC. - MI 0695 HUDSON MI
— 517-451 0XXX1XXX3XXX6XXX7XXX · 5 holders which blocks → FRONTIER NORTH, INC. - MI 0695 BRITTON MI
— 517-456 0XXX3XXX5XXX · 3 holders which blocks → FRONTIER NORTH, INC. - MI 0695 CLINTON MI
— 517-486 1XXX which blocks → FRONTIER NORTH, INC. - MI 0695 BLISSFIELD MI
— 517-522 0XXX1XXX2XXX7XXX9XXX · 5 holders which blocks → FRONTIER NORTH, INC. - MI 0695 GRASS LAKE MI
— 517-622 9XXX which blocks → FRONTIER NORTH, INC. - MI 0695 GRANDLEDGE MI
— 517-626 0XXX1XXX3XXX4XXX8XXX9XXX · 4 holders which blocks → FRONTIER NORTH, INC. - MI 0695 GRANDLEDGE MI
— 517-627 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 GRANDLEDGE MI
— 517-639 0XXX1XXX2XXX6XXX · 3 holders which blocks → FRONTIER NORTH, INC. - MI 0695 QUINCY MI
— 517-641 0XXX1XXX2XXX3XXX5XXX9XXX · 6 holders which blocks → FRONTIER NORTH, INC. - MI 0695 BATH MI
— 517-651 0XXX4XXX8XXX · 3 holders which blocks → FRONTIER NORTH, INC. - MI 0695 LAINGSBURG MI
— 517-655 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 WILLIAMSTN MI
— 517-668 4XXX5XXX6XXX7XXX · 4 holders which blocks → FRONTIER NORTH, INC. - MI 0695 DE WITT MI
— 517-669 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 DE WITT MI
— 517-741 0XXX6XXX · 2 holders which blocks → FRONTIER NORTH, INC. - MI 0695 UNION CITY MI
— 517-815 1XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 6 holders which blocks → FRONTIER NORTH, INC. - MI 0695 TECUMSEH MI

Source: NANPA CO Code Assignments (Utilized, All States, Public), file date 09/25/2026 — Tier A primary source, refreshed on every import. Viewing is free; bulk downloads require a membership.