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
— 510-492 3XXX6XXX · 2 holders which blocks → PACIFIC BELL 9740 FRNK OLIVR CA
— 510-494 not yet reported which blocks → PACIFIC BELL 9740 FRNK MAIN CA
— 510-495 0XXX1XXX4XXX5XXX6XXX7XXX9XXX · 4 holders which blocks → PACIFIC BELL 9740 OKLD BKLY CA
— 510-498 5XXX6XXX which blocks → PACIFIC BELL 9740 FRNK OLIVR CA
— 510-505 4XXX8XXX · 2 holders which blocks → PACIFIC BELL 9740 FRNK MAIN CA
— 510-521 not yet reported which blocks → PACIFIC BELL 9740 OKLD ALMD CA
— 510-522 not yet reported which blocks → PACIFIC BELL 9740 OKLD ALMD CA
— 510-523 not yet reported which blocks → PACIFIC BELL 9740 OKLD ALMD CA
— 510-524 not yet reported which blocks → PACIFIC BELL 9740 OKLD BKLY CA
— 510-525 not yet reported which blocks → PACIFIC BELL 9740 OKLD BKLY CA
— 510-526 not yet reported which blocks → PACIFIC BELL 9740 OKLD BKLY CA
— 510-527 not yet reported which blocks → PACIFIC BELL 9740 OKLD BKLY CA
— 510-528 not yet reported which blocks → PACIFIC BELL 9740 OKLD BKLY CA
— 510-529 1XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 5 holders which blocks → PACIFIC BELL 9740 OKLD BKLY CA
— 510-530 not yet reported which blocks → PACIFIC BELL 9740 OKLD FRTVL CA
— 510-531 not yet reported which blocks → PACIFIC BELL 9740 OKLD FRTVL CA
— 510-532 not yet reported which blocks → PACIFIC BELL 9740 OKLD FRTVL CA
— 510-533 not yet reported which blocks → PACIFIC BELL 9740 OKLD FRTVL CA
— 510-534 not yet reported which blocks → PACIFIC BELL 9740 OKLD FRTVL CA
— 510-535 not yet reported which blocks → PACIFIC BELL 9740 OKLD FRTVL CA
— 510-536 not yet reported which blocks → PACIFIC BELL 9740 OKLD FRTVL CA
— 510-537 not yet reported which blocks → PACIFIC BELL 9740 HAYWARD CA
— 510-538 not yet reported which blocks → PACIFIC BELL 9740 HAYWARD CA
— 510-540 not yet reported which blocks → PACIFIC BELL 9740 OKLD BKLY CA
— 510-547 not yet reported which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-548 not yet reported which blocks → PACIFIC BELL 9740 OKLD BKLY CA
— 510-549 6XXX7XXX · 2 holders which blocks → PACIFIC BELL 9740 OKLD BKLY CA
— 510-553 not yet reported which blocks → PACIFIC BELL 9740 OKLD TRNID CA
— 510-558 5XXX which blocks → PACIFIC BELL 9740 OKLD BKLY CA
— 510-559 0XXX which blocks → PACIFIC BELL 9740 OKLD BKLY CA
— 510-562 not yet reported which blocks → PACIFIC BELL 9740 OKLD TRNID CA
— 510-563 0XXX7XXX9XXX · 2 holders which blocks → PACIFIC BELL 9740 OKLD TRNID CA
— 510-567 3XXX4XXX7XXX · 3 holders which blocks → PACIFIC BELL 9740 OKLD TRNID CA
— 510-568 not yet reported which blocks → PACIFIC BELL 9740 OKLD TRNID CA
— 510-569 not yet reported which blocks → PACIFIC BELL 9740 OKLD TRNID CA
— 510-574 5XXX6XXX7XXX8XXX9XXX · 3 holders which blocks → PACIFIC BELL 9740 FRNK MAIN CA
— 510-577 not yet reported which blocks → PACIFIC BELL 9740 OKLD TRNID CA
— 510-581 not yet reported which blocks → PACIFIC BELL 9740 HAYWARD CA
— 510-582 not yet reported which blocks → PACIFIC BELL 9740 HAYWARD CA
— 510-583 not yet reported which blocks → PACIFIC BELL 9740 HAYWARD CA
— 510-587 9XXX which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-594 not yet reported which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-595 not yet reported which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-596 5XXX which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-597 2XXX which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-601 2XXX which blocks → PACIFIC BELL 9740 OKLD MN-PD CA
— 510-608 2XXX which blocks → PACIFIC BELL 9740 FRNK MAIN CA
— 510-613 3XXX4XXX5XXX · 2 holders which blocks → PACIFIC BELL 9740 OKLD TRNID CA
— 510-614 not yet reported which blocks → PACIFIC BELL 9740 OKLD TRNID CA
— 510-615 not yet reported which blocks → PACIFIC BELL 9740 OKLD TRNID 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.