NumberResearch Membership · Data 09/19/2026

Recent prefix assignments

0 prefixes assigned in the last 30 days · from the daily NANPA CO code file, 09/19/2026

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 231
FRONTIER NORTH, INC. - MI 52
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
2001-06-18 231-646 4XXX6XXX7XXX8XXX · 4 holders which blocks → FRONTIER NORTH, INC. - MI 0695 ELLSWORTH MI
2001-06-18 231-681 1XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX · 4 holders which blocks → FRONTIER NORTH, INC. - MI 0695 FRUITPORT MI
— 231-322 0XXX1XXX3XXX5XXX7XXX8XXX9XXX · 5 holders which blocks → FRONTIER NORTH, INC. - MI 0695 TRCHRIVBDG MI
— 231-331 0XXX1XXX2XXX3XXX5XXX8XXX9XXX · 5 holders which blocks → FRONTIER NORTH, INC. - MI 0695 ALDEN MI
— 231-377 0XXX1XXX2XXX3XXX5XXX8XXX · 5 holders which blocks → FRONTIER NORTH, INC. - MI 0695 CLAM RIVER MI
— 231-533 0XXX1XXX2XXX · 2 holders which blocks → FRONTIER NORTH, INC. - MI 0695 BELLAIRE MI
— 231-544 0XXX1XXX7XXX · 3 holders which blocks → FRONTIER NORTH, INC. - MI 0695 CENTRAL LK MI
— 231-571 0XXX1XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX · 3 holders which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-588 0XXX1XXX3XXX5XXX7XXX8XXX · 4 holders which blocks → FRONTIER NORTH, INC. - MI 0695 ELLSWORTH MI
— 231-599 0XXX1XXX4XXX5XXX6XXX7XXX8XXX9XXX · 4 holders which blocks → FRONTIER NORTH, INC. - MI 0695 EASTPORT MI
— 231-719 5XXX6XXX7XXX · 2 holders which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-720 0XXX4XXX5XXX6XXX8XXX9XXX · 3 holders which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-722 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-724 0XXX which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-725 5XXX which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-726 0XXX7XXX8XXX · 3 holders which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-727 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-728 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-733 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-736 0XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-737 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-739 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-744 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-747 0XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 3 holders which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-755 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-759 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-760 0XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 5 holders which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-766 1XXX6XXX7XXX8XXX · 3 holders which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-767 5XXX6XXX · 2 holders which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-769 0XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 3 holders which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-773 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-777 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-780 7XXX8XXX which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-788 8XXX9XXX · 2 holders which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-798 5XXX which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-799 5XXX which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-821 3XXX4XXX5XXX6XXX7XXX8XXX · 5 holders which blocks → FRONTIER NORTH, INC. - MI 0695 HOLTON MI
— 231-823 1XXX4XXX5XXX7XXX · 4 holders which blocks → FRONTIER NORTH, INC. - MI 0695 STANWOOD MI
— 231-828 0XXX1XXX2XXX3XXX7XXX8XXX9XXX · 5 holders which blocks → FRONTIER NORTH, INC. - MI 0695 TWIN LAKE MI
— 231-830 4XXX5XXX6XXX7XXX which blocks → FRONTIER NORTH, INC. - MI 0695 MUSKEGON MI
— 231-843 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 LUDINGTON MI
— 231-845 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 LUDINGTON MI
— 231-853 1XXX3XXX4XXX7XXX9XXX · 4 holders which blocks → FRONTIER NORTH, INC. - MI 0695 RAVENNA MI
— 231-854 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 HESPERIA MI
— 231-861 1XXX9XXX · 2 holders which blocks → FRONTIER NORTH, INC. - MI 0695 SHELBY MI
— 231-865 9XXX which blocks → FRONTIER NORTH, INC. - MI 0695 FRUITPORT MI
— 231-869 1XXX3XXX · 2 holders which blocks → FRONTIER NORTH, INC. - MI 0695 PENTWATER MI
— 231-873 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 HART MI
— 231-893 not yet reported which blocks → FRONTIER NORTH, INC. - MI 0695 WHITEHALL MI
— 231-894 0XXX which blocks → FRONTIER NORTH, INC. - MI 0695 WHITEHALL MI

Source: NANPA CO Code Assignments (Utilized, All States, Public), file date 09/19/2026 — Tier A primary source, refreshed on every import. Viewing is free; bulk downloads require a membership.