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 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
2012-11-30 510-454 0–9 XXXall 10 · 4 holders which blocks → PACIFIC BELL 9740 OKLD TRNID CA
2009-11-25 510-408 0–9 XXXall 10 · 3 holders which blocks → PACIFIC BELL 9740 ELSBR-PINL CA
2007-11-28 510-356 0–9 XXXall 10 · 5 holders which blocks → PACIFIC BELL 9740 OKLD BKLY CA
— 510-204 not yet reported which blocks → PACIFIC BELL 9740 OKLD BKLY CA
— 510-208 not yet reported which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-215 not yet reported which blocks → PACIFIC BELL 9740 RICHMOND CA
— 510-222 not yet reported which blocks → PACIFIC BELL 9740 ELSBR-PINL CA
— 510-223 not yet reported which blocks → PACIFIC BELL 9740 ELSBR-PINL CA
— 510-226 not yet reported which blocks → PACIFIC BELL 9740 FRNK OLIVR CA
— 510-229 0XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 4 holders which blocks → PACIFIC BELL 9740 OKLD BKLY CA
— 510-231 not yet reported which blocks → PACIFIC BELL 9740 RICHMOND CA
— 510-232 not yet reported which blocks → PACIFIC BELL 9740 RICHMOND CA
— 510-233 not yet reported which blocks → PACIFIC BELL 9740 RICHMOND CA
— 510-234 not yet reported which blocks → PACIFIC BELL 9740 RICHMOND CA
— 510-235 not yet reported which blocks → PACIFIC BELL 9740 RICHMOND CA
— 510-236 not yet reported which blocks → PACIFIC BELL 9740 RICHMOND CA
— 510-237 not yet reported which blocks → PACIFIC BELL 9740 RICHMOND CA
— 510-238 not yet reported which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-242 not yet reported which blocks → PACIFIC BELL 9740 RICHMOND CA
— 510-243 4XXX5XXX · 2 holders which blocks → PACIFIC BELL 9740 ELSBR-PINL CA
— 510-245 not yet reported which blocks → PACIFIC BELL 9740 HRCUL-RODE CA
— 510-247 none assigned yet which blocks → PACIFIC BELL 9740 HAYWARD CA
— 510-249 not yet reported which blocks → PACIFIC BELL 9740 FRNK OLIVR CA
— 510-251 not yet reported which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-252 not yet reported which blocks → PACIFIC BELL 9740 FRNK OLIVR CA
— 510-258 1XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 3 holders which blocks → PACIFIC BELL 9740 HAYWARD CA
— 510-259 8XXX9XXX · 2 holders which blocks → PACIFIC BELL 9740 HAYWARD CA
— 510-261 not yet reported which blocks → PACIFIC BELL 9740 OKLD FRTVL CA
— 510-262 3XXX6XXX · 2 holders which blocks → PACIFIC BELL 9740 ELSBR-PINL CA
— 510-263 3XXX5XXX6XXX7XXX8XXX9XXX · 4 holders which blocks → PACIFIC BELL 9740 OKLD ALMD CA
— 510-264 2XXX7XXX · 2 holders which blocks → PACIFIC BELL 9740 HAYWARD CA
— 510-265 4XXX9XXX which blocks → PACIFIC BELL 9740 HAYWARD CA
— 510-266 2XXX4XXX8XXX9XXX · 4 holders which blocks → PACIFIC BELL 9740 HAYWARD CA
— 510-267 not yet reported which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-268 6XXX which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-271 not yet reported which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-272 7XXX8XXX which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-273 not yet reported which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-276 not yet reported which blocks → PACIFIC BELL 9740 HAYWARD CA
— 510-278 not yet reported which blocks → PACIFIC BELL 9740 HAYWARD CA
— 510-284 2XXX3XXX5XXX7XXX8XXX9XXX · 5 holders which blocks → PACIFIC BELL 9740 FRNK MAIN 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
— 510-292 0XXX1XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 3 holders which blocks → PACIFIC BELL 9740 OKLD BKLY CA
— 510-293 6XXX which blocks → PACIFIC BELL 9740 HAYWARD CA
— 510-297 not yet reported which blocks → PACIFIC BELL 9740 OKLD TRNID CA
— 510-302 5XXX7XXX8XXX9XXX which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-307 5XXX6XXX · 2 holders which blocks → PACIFIC BELL 9740 RICHMOND CA
— 510-317 not yet reported which blocks → PACIFIC BELL 9740 HAYWARD CA
— 510-324 5XXX6XXX7XXX9XXX · 4 holders which blocks → PACIFIC BELL 9740 FRNK GRNLF 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.