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
NEW CINGULAR WIRELESS PCS, LLC - IL 72
MICHIGAN BELL TEL CO 72
FRONTIER NORTH, INC. - MI 52
ONVOY, LLCV - MI 49
TELNET WORLDWIDE, INC. 43
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
2016-07-29 231-495 0XXX1XXX3XXX4XXX5XXX7XXX8XXX9XXX · 5 holders which blocks → NEW CINGULAR WIRELESS PCS, LLC - IL 6534 BELLAIRE MI
2016-07-25 231-212 0XXX1XXX3XXX5XXX7XXX9XXX · 4 holders which blocks → CENTURYLINK COMMUNICATIONS, LLC 508J INTERLOCHN MI
2016-04-18 231-252 0–9 XXXall 10 · 4 holders which blocks → BANDWIDTH.COM CLEC, LLC - MI 991E TRAVERSECY MI
2016-03-22 231-277 0–9 XXXall 10 · 5 holders which blocks → ONVOY, LLCV - MI 543C FOUNTAIN MI
2016-03-22 231-771 0XXX1XXX2XXX3XXX4XXX5XXX · 3 holders which blocks → ONVOY, LLCV - MI 543C ELK RAPIDS MI
2016-02-29 231-280 0XXX1XXX2XXX3XXX5XXX7XXX9XXX · 6 holders which blocks → ONVOY, LLCV - MI 543C MANCELONA MI
2016-02-25 231-707 0XXX1XXX2XXX3XXX5XXX6XXX7XXX8XXX9XXX · 4 holders which blocks → ONVOY, LLCV - MI 543C NEWAYGO MI
2015-12-22 231-246 0–9 XXXall 10 · 6 holders which blocks → COMCAST IP PHONE, LLC 318J MUSKEGON MI
2015-12-07 231-234 1XXX which blocks → CHARTER IP ENABLED SERVICES, LLC 792K BUCKLEY MI
2015-12-02 231-251 0XXX1XXX2XXX3XXX4XXX5XXX7XXX8XXX9XXX · 3 holders which blocks → PEERLESS NETWORK OF MICHIGAN, LLC - MI 933G LKLEELANAU MI
2015-12-02 231-447 0XXX1XXX2XXX3XXX4XXX5XXX6XXX7XXX9XXX · 3 holders which blocks → ONVOY, LLCV - MI 543C HOLTON MI
2015-12-01 231-216 0–9 XXXall 10 · 5 holders which blocks → PEERLESS NETWORK OF MICHIGAN, LLC - MI 933G FRANKFORT MI
2015-12-01 231-442 0XXX1XXX2XXX3XXX5XXX6XXX7XXX8XXX9XXX · 6 holders which blocks → PEERLESS NETWORK OF MICHIGAN, LLC - MI 933G HARRIETTA MI
2015-08-26 231-244 0–9 XXXall 10 · 4 holders which blocks → CENTURYLINK COMMUNICATIONS, LLC 508J BOYNE CITY MI
2015-08-25 231-422 0XXX1XXX2XXX3XXX4XXX5XXX7XXX8XXX9XXX · 5 holders which blocks → CENTURYLINK COMMUNICATIONS, LLC 508J PELLSTON MI
2015-08-24 231-444 0–9 XXXall 10 · 7 holders which blocks → ONVOY, LLCV - MI 543C CADILLAC MI
2015-08-24 231-999 1XXX2XXX3XXX4XXX5XXX7XXX8XXX9XXX · 5 holders which blocks → ONVOY, LLCV - MI 543C CENTRAL LK MI
2015-06-16 231-888 0XXX1XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX · 5 holders which blocks → ONVOY, LLCV - MI 543C TWIN LAKE MI
2015-06-01 231-221 0–9 XXXall 10 · 5 holders which blocks → CENTURYLINK COMMUNICATIONS, LLC 508J HARBOR SPG MI
2015-04-21 231-489 0–9 XXXall 10 · 7 holders which blocks → PENINSULA FIBER NETWORK, LLC - MI 116F PETOSKEY MI
2015-03-26 231-213 0–9 XXXwhole prefix which blocks → MICHIGAN BELL TEL CO 9323 TRAVERSECY MI
2014-12-19 231-655 0–9 XXXall 10 · 5 holders which blocks → CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MI 6003 MANISTEE MI
2014-11-07 231-787 0–9 XXXall 10 · 4 holders which blocks → ONVOY, LLCV - MI 543C WHITECLOUD MI
2014-10-06 231-751 0–9 XXXall 10 · 4 holders which blocks → ONVOY, LLCV - MI 543C WALLOON LK MI
2014-10-06 231-819 0–9 XXXall 10 · 4 holders which blocks → ONVOY, LLCV - MI 543C TUSTIN MI
2014-09-26 231-434 0–9 XXXall 10 · 4 holders which blocks → NEW CINGULAR WIRELESS PCS, LLC - IL 6534 MANTON MI
2014-09-25 231-685 0XXX1XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX · 6 holders which blocks → CHARTER IP ENABLED SERVICES, LLC 792K RAVENNA MI
2014-05-19 231-265 0XXX1XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX · 4 holders which blocks → CHARTER IP ENABLED SERVICES, LLC 792K CORAL MI
2013-08-07 231-484 0–9 XXXall 10 · 6 holders which blocks → TELEPORT COMMUNICATIONS AMERICA, LLC - MI 770E EASTJORDAN MI
2012-09-26 231-227 0XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 3 holders which blocks → CHARTER IP ENABLED SERVICES, LLC 792K HONOR MI
2012-09-26 231-295 7XXX which blocks → CHARTER IP ENABLED SERVICES, LLC 792K LAKE CITY MI
2012-09-26 231-359 0XXX2XXX3XXX4XXX5XXX6XXX7XXX9XXX · 3 holders which blocks → CHARTER IP ENABLED SERVICES, LLC 792K MECOSTA MI
2012-09-26 231-626 0XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 6 holders which blocks → CHARTER IP ENABLED SERVICES, LLC 792K LEVERING MI
2012-08-01 231-559 0–9 XXXall 10 · 6 holders which blocks → BANDWIDTH.COM CLEC, LLC - MI 991E MCBAIN MI
2012-05-11 231-291 0–9 XXXwhole prefix which blocks → TELNET WORLDWIDE, INC. 817J MUSKEGON MI
2011-12-28 231-299 0–9 XXXall 10 · 6 holders which blocks → METROPCS, INC. 5562 MANISTEE MI
2011-08-17 231-427 0–9 XXXall 10 · 6 holders which blocks → AT&T ENTERPRISES, LLC 516C MACKINAWCY MI
2011-08-16 231-403 0–9 XXXall 10 · 6 holders which blocks → AT&T ENTERPRISES, LLC 516C WILLIAMSBG MI
2011-05-16 231-303 0–9 XXXall 10 · 8 holders which blocks → TELEPORT COMMUNICATIONS AMERICA, LLC - MI 770E NEWAYGO MI
2011-04-29 231-433 1XXX3XXX4XXX9XXX · 3 holders which blocks → CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MI 6003 MOORESTOWN MI
2010-10-11 231-412 0–9 XXXall 10 · 4 holders which blocks → BANDWIDTH.COM CLEC, LLC - MI 991E HARBOR SPG MI
2010-07-30 231-292 0XXX1XXX2XXX3XXX5XXX6XXX7XXX8XXX9XXX · 5 holders which blocks → CHARTER IP ENABLED SERVICES, LLC 792K WHITEHALL MI
2009-07-17 231-245 0–9 XXXall 10 · 4 holders which blocks → NEW CINGULAR WIRELESS PCS, LLC - IL 6534 NEWAYGO MI
2008-06-03 231-508 0–9 XXXall 10 · 6 holders which blocks → KALEVA TELEPHONE COMPANY - MI 392F ONEKAMA MI
2007-02-07 231-259 0–9 XXXall 10 · 8 holders which blocks → CHARTER IP ENABLED SERVICES, LLC 792K SHELBY MI
2006-10-10 231-241 0–9 XXXall 10 · 3 holders which blocks → DAYSTARR LLC DBA DAYSTARR COMMUNICATIONS 993L PENTWATER MI
2005-09-13 231-288 0–9 XXXall 10 · 2 holders which blocks → NEW CINGULAR WIRELESS PCS, LLC - IL 6534 MUSKEGON MI
2005-04-11 231-833 0XXX1XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX · 4 holders which blocks → NEW CINGULAR WIRELESS PCS, LLC - IL 6534 WOLVERINE MI
2005-01-27 231-424 2XXX4XXX7XXX · 2 holders which blocks → ACD TELECOM, INC. - MI 3535 CARR MI
2005-01-21 231-262 0–9 XXXall 10 · 5 holders which blocks → ACD TELECOM, INC. - MI 3535 ELMIRA 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.