NumberResearch Membership · Data 09/20/2026

Recent prefix assignments

0 prefixes assigned in the last 30 days · from the daily NANPA CO code file, 09/20/2026

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
— 510-336 4XXX5XXX6XXX8XXX · 2 holders which blocks → PACIFIC BELL 9740 OKLD FRTVL CA
— 510-337 4XXX which blocks → PACIFIC BELL 9740 OKLD ALMD CA
— 510-338 2XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 7 holders which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-339 not yet reported which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-346 5XXX6XXX9XXX · 2 holders which blocks → PACIFIC BELL 9740 OKLD TRNID CA
— 510-347 7XXX8XXX9XXX · 3 holders which blocks → PACIFIC BELL 9740 OKLD TRNID CA
— 510-351 not yet reported which blocks → PACIFIC BELL 9740 OKLD TRNID CA
— 510-352 not yet reported which blocks → PACIFIC BELL 9740 OKLD TRNID CA
— 510-353 3XXX which blocks → PACIFIC BELL 9740 FRNK OLIVR CA
— 510-354 not yet reported which blocks → PACIFIC BELL 9740 FRNK OLIVR CA
— 510-357 not yet reported which blocks → PACIFIC BELL 9740 OKLD TRNID CA
— 510-360 not yet reported which blocks → PACIFIC BELL 9740 FRNK OLIVR CA
— 510-374 0XXX2XXX4XXX5XXX6XXX8XXX9XXX · 5 holders which blocks → PACIFIC BELL 9740 RICHMOND CA
— 510-382 not yet reported which blocks → PACIFIC BELL 9740 OKLD TRNID CA
— 510-383 0XXX6XXX7XXX · 3 holders which blocks → PACIFIC BELL 9740 OKLD TRNID CA
— 510-412 not yet reported which blocks → PACIFIC BELL 9740 RICHMOND CA
— 510-413 2XXX3XXX6XXX7XXX8XXX · 4 holders which blocks → PACIFIC BELL 9740 FRNK OLIVR CA
— 510-419 7XXX9XXX · 2 holders which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-420 not yet reported which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-425 none assigned yet which blocks → PACIFIC BELL 9740 OKLD TRNID CA
— 510-428 not yet reported which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-429 not yet reported which blocks → PACIFIC BELL 9740 FRNK GRNLF CA
— 510-430 not yet reported which blocks → PACIFIC BELL 9740 OKLD TRNID CA
— 510-433 8XXX which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-434 4XXX6XXX8XXX which blocks → PACIFIC BELL 9740 OKLD FRTVL CA
— 510-436 not yet reported which blocks → PACIFIC BELL 9740 OKLD FRTVL CA
— 510-437 0XXX which blocks → PACIFIC BELL 9740 OKLD FRTVL CA
— 510-438 1XXX3XXX which blocks → PACIFIC BELL 9740 FRNK OLIVR CA
— 510-440 2XXX3XXX5XXX7XXX · 4 holders which blocks → PACIFIC BELL 9740 FRNK OLIVR CA
— 510-441 4XXX which blocks → PACIFIC BELL 9740 FRNK GRNLF CA
— 510-444 9XXX which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-445 3XXX7XXX8XXX9XXX · 2 holders which blocks → PACIFIC BELL 9740 FRNK OLIVR CA
— 510-446 8XXX which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-450 not yet reported which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-451 not yet reported which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-452 7XXX which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-464 0XXX which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-465 not yet reported which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-466 1XXX which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-471 not yet reported which blocks → PACIFIC BELL 9740 FRNK GRNLF CA
— 510-475 not yet reported which blocks → PACIFIC BELL 9740 FRNK GRNLF CA
— 510-476 9XXX which blocks → PACIFIC BELL 9740 FRNK GRNLF CA
— 510-477 not yet reported which blocks → PACIFIC BELL 9740 FRNK GRNLF CA
— 510-481 not yet reported which blocks → PACIFIC BELL 9740 HAYWARD CA
— 510-482 not yet reported which blocks → PACIFIC BELL 9740 OKLD FRTVL CA
— 510-483 not yet reported which blocks → PACIFIC BELL 9740 OKLD TRNID CA
— 510-486 not yet reported which blocks → PACIFIC BELL 9740 OKLD BKLY CA
— 510-487 not yet reported which blocks → PACIFIC BELL 9740 FRNK GRNLF CA
— 510-489 not yet reported which blocks → PACIFIC BELL 9740 FRNK GRNLF CA
— 510-490 not yet reported which blocks → PACIFIC BELL 9740 FRNK OLIVR CA

Source: NANPA CO Code Assignments (Utilized, All States, Public), file date 09/20/2026 — Tier A primary source, refreshed on every import. Viewing is free; bulk downloads require a membership.