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 585
FRONTIER TELEPHONE OF ROCHESTER, INC. 186
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
2018-04-10 585-602 0–9 XXXwhole prefix which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
2011-02-25 585-626 0–9 XXXall 10 · 5 holders which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 WEBSTER NY
2009-07-07 585-666 0–9 XXXall 10 · 3 holders which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
2009-07-01 585-500 0–9 XXXall 10 · 4 holders which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
2008-07-15 585-351 0–9 XXXall 10 · 5 holders which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
2006-10-05 585-678 0–9 XXXall 10 · 5 holders which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 FAIRPORT NY
2005-05-17 585-753 0–9 XXXwhole prefix which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
2004-08-19 585-413 0–9 XXXall 10 · 4 holders which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
2003-09-29 585-278 0–9 XXXall 10 · 4 holders which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-214 9XXX which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-216 1XXX3XXX4XXX5XXX7XXX8XXX · 4 holders which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 WEBSTER NY
— 585-217 0XXX1XXX2XXX3XXX6XXX7XXX · 2 holders which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 WEBSTER NY
— 585-218 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 EROCHESTER NY
— 585-220 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-221 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 XXXXXXXXXX NY
— 585-222 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-223 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 FAIRPORT NY
— 585-224 5XXX6XXX which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-225 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-226 0XXX1XXX7XXX · 3 holders which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 AVON NY
— 585-227 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-231 none assigned yet which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-232 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-234 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-235 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-237 1XXX8XXX · 2 holders which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 PERRY NY
— 585-238 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-239 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-240 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-241 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-242 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-243 8XXX which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 GENESEO NY
— 585-244 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-245 0XXX1XXX2XXX3XXX4XXX · 2 holders which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 GENESEO NY
— 585-246 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-247 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-248 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 EROCHESTER NY
— 585-249 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 EROCHESTER NY
— 585-251 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-253 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-254 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-255 0XXX which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-256 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-258 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-262 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-263 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-264 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 EROCHESTER NY
— 585-265 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 WEBSTER NY
— 585-266 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY
— 585-271 not yet reported which blocks → FRONTIER TELEPHONE OF ROCHESTER, INC. 0121 ROCHESTER NY

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.