NumberResearchRecent prefix assignments
0 prefixes assigned in the last 30 days · from the daily NANPA CO code file, 09/20/2026
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.
| Assigned | NPA-NXX | Thousands-blocks taken (last-4 opening) | Code holder | OCN | Rate center | State |
|---|---|---|---|---|---|---|
| — | 203-513 | 0XXX1XXX2XXX3XXX4XXX5XXX7XXX8XXX9XXX · 5 holders which blocks → | AT&T - LOCAL | 7421 | HUNTINGTON | CT |
| — | 203-529 | 0XXX1XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX · 6 holders which blocks → | AT&T - LOCAL | 7421 | WILTON | CT |
| — | 203-542 | 0XXX1XXX2XXX4XXX5XXX6XXX7XXX8XXX9XXX · 5 holders which blocks → | AT&T - LOCAL | 7421 | GREENWICH | CT |
| — | 203-564 | 0XXX2XXX3XXX4XXX6XXX7XXX8XXX9XXX · 5 holders which blocks → | AT&T - LOCAL | 7421 | STAMFORD | CT |
| — | 203-571 | 0XXX1XXX2XXX3XXX4XXX6XXX7XXX8XXX9XXX · 6 holders which blocks → | AT&T - LOCAL | 7421 | WESTPORT | CT |
| — | 203-626 | 0XXX1XXX2XXX4XXX5XXX6XXX7XXX8XXX9XXX · 3 holders which blocks → | AT&T - LOCAL | 7421 | WALLINGFD | CT |
| — | 203-673 | 1XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 2 holders which blocks → | AT&T - LOCAL | 7421 | BRIDGEPORT | CT |
| — | 203-689 | 0XXX1XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX · 5 holders which blocks → | AT&T - LOCAL | 7421 | GUILFORD | CT |
| — | 203-701 | 0XXX1XXX2XXX4XXX5XXX6XXX7XXX8XXX9XXX · 5 holders which blocks → | AT&T - LOCAL | 7421 | MILFORD | CT |
| — | 203-822 | 0XXX1XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX · 4 holders which blocks → | AT&T - LOCAL | 7421 | NORWALK | CT |
| — | 203-868 | 0XXX1XXX2XXX4XXX5XXX6XXX7XXX8XXX9XXX · 3 holders which blocks → | AT&T - LOCAL | 7421 | NEW HAVEN | CT |
| — | 203-875 | 0XXX1XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX · 2 holders which blocks → | AT&T - LOCAL | 7421 | DARIEN | CT |
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.