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 510
PACIFIC BELL 278
NEW CINGULAR WIRELESS PCS, LLC 78
T-MOBILE USA, INC. 65
CELLCO PARTNERSHIP DBA VERIZON WIRELESS - CA 60
METROPCS, INC. 45
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
— 510-273 not yet reported which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-274 0–9 XXXall 10 · 8 holders which blocks → UTILITY TELECOM GROUP, LLC - CA 9262 HAYWARD CA
— 510-275 2XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 6 holders which blocks → ONVOY, LLC - CA 649C ELSBR-PINL CA
— 510-276 not yet reported which blocks → PACIFIC BELL 9740 HAYWARD CA
— 510-277 2XXX4XXX5XXX6XXX7XXX8XXX9XXX · 6 holders which blocks → LEVEL 3 COMMUNICATIONS, LLC - CA 8826 OKLD BKLY CA
— 510-278 not yet reported which blocks → PACIFIC BELL 9740 HAYWARD CA
— 510-279 3XXX4XXX6XXX8XXX9XXX · 3 holders which blocks → LEVEL 3 COMMUNICATIONS, LLC - CA 8826 FRNK OLIVR CA
— 510-280 0XXX3XXX4XXX5XXX7XXX8XXX9XXX · 3 holders which blocks → MCIMETRO ACCESS TRANSMISSION SERVICES LLC 7229 OKLD BKLY CA
— 510-281 not yet reported which blocks → ONVOY, LLC - CA 649C OKLD MN-PD CA
— 510-283 1XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 5 holders which blocks → MCIMETRO ACCESS TRANSMISSION SERVICES LLC 7229 ELSBR-PINL CA
— 510-284 2XXX3XXX5XXX7XXX8XXX9XXX · 5 holders which blocks → PACIFIC BELL 9740 FRNK MAIN CA
— 510-285 6XXX7XXX8XXX · 3 holders which blocks → MCIMETRO ACCESS TRANSMISSION SERVICES LLC - CA 7240 OKLD MN-PD CA
— 510-286 not yet reported which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-287 6XXX which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-288 not yet reported which blocks → ONVOY, LLC - CA 649C OKLD MN-PD CA
— 510-289 not yet reported which blocks → NEW CINGULAR WIRELESS PCS, LLC 6010 OKLD MN-PD CA
— 510-290 none assigned yet which blocks → T-MOBILE USA, INC. 6529 OKLD MN-PD CA
— 510-291 4XXX which blocks → ONVOY, LLC - CA 649C OKLD MN-PD CA
— 510-292 0XXX1XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 3 holders which blocks → PACIFIC BELL 9740 OKLD BKLY CA
— 510-293 6XXX which blocks → PACIFIC BELL 9740 HAYWARD CA
— 510-295 3XXX4XXX5XXX7XXX8XXX9XXX · 2 holders which blocks → CELLCO PARTNERSHIP DBA VERIZON WIRELESS - CA 6006 OKLD BKLY CA
— 510-296 0–9 XXXall 10 · 4 holders which blocks → LEVEL 3 COMMUNICATIONS, LLC - CA 8826 HRCUL-RODE CA
— 510-297 not yet reported which blocks → PACIFIC BELL 9740 OKLD TRNID CA
— 510-299 not yet reported which blocks → CELLCO PARTNERSHIP DBA VERIZON WIRELESS - CA 6006 FRNK MAIN CA
— 510-300 4XXX5XXX7XXX · 2 holders which blocks → U.S. TELEPACIFIC CORP. DBA TPX COMMUNICATIONS 671J HAYWARD CA
— 510-301 not yet reported which blocks → CELLCO PARTNERSHIP DBA VERIZON WIRELESS - CA 6006 OKLD MN-PD CA
— 510-302 5XXX7XXX8XXX9XXX which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-303 not yet reported which blocks → NEW CINGULAR WIRELESS PCS, LLC 6010 HAYWARD CA
— 510-304 not yet reported which blocks → NEW CINGULAR WIRELESS PCS, LLC 6010 FRNK MAIN CA
— 510-305 not yet reported which blocks → NEW CINGULAR WIRELESS PCS, LLC 6010 HAYWARD CA
— 510-306 1XXX2XXX3XXX4XXX5XXX7XXX8XXX9XXX · 4 holders which blocks → METROPCS, INC. 5562 OKLD ALMD CA
— 510-307 5XXX6XXX · 2 holders which blocks → PACIFIC BELL 9740 RICHMOND CA
— 510-308 not yet reported which blocks → SPOK, INC. 6630 OKLD MN-PD CA
— 510-311 not yet reported which blocks → MULTIPLE OCN LISTING MULT XXXXXXXXXX CA
— 510-313 1XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX · 3 holders which blocks → TELEPORT COMMUNICATIONS AMERICA, LLC - CA 7145 HRCUL-RODE CA
— 510-315 not yet reported which blocks → LEVEL 3 COMMUNICATIONS, LLC - CA 8826 HAYWARD CA
— 510-316 none assigned yet which blocks → NEW CINGULAR WIRELESS PCS, LLC 6010 OKLD MN-PD CA
— 510-317 not yet reported which blocks → PACIFIC BELL 9740 HAYWARD CA
— 510-318 3XXX5XXX6XXX7XXX8XXX9XXX · 3 holders which blocks → CELLCO PARTNERSHIP DBA VERIZON WIRELESS - CA 6006 OKLD MN-PD CA
— 510-321 not yet reported which blocks → SPOK, INC. 6630 OKLD MN-PD CA
— 510-322 0XXX1XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX · 2 holders which blocks → MCIMETRO ACCESS TRANSMISSION SERVICES LLC 7229 HRCUL-RODE CA
— 510-323 2XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 5 holders which blocks → MCIMETRO ACCESS TRANSMISSION SERVICES LLC 7229 RICHMOND CA
— 510-324 5XXX6XXX7XXX9XXX · 4 holders which blocks → PACIFIC BELL 9740 FRNK GRNLF CA
— 510-325 not yet reported which blocks → NEW CINGULAR WIRELESS PCS, LLC 6010 OKLD MN-PD CA
— 510-326 not yet reported which blocks → NEW CINGULAR WIRELESS PCS, LLC 6010 OKLD MN-PD CA
— 510-327 1XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 6 holders which blocks → ONVOY, LLC - CA 649C HRCUL-RODE CA
— 510-329 not yet reported which blocks → NEW CINGULAR WIRELESS PCS, LLC 6010 HAYWARD CA
— 510-331 not yet reported which blocks → NEW CINGULAR WIRELESS PCS, LLC 6010 HAYWARD CA
— 510-332 not yet reported which blocks → NEW CINGULAR WIRELESS PCS, LLC 6010 OKLD MN-PD CA
— 510-333 not yet reported which blocks → NEW CINGULAR WIRELESS PCS, LLC 6010 OKLD MN-PD CA

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.