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 |
|---|---|---|---|---|---|---|
| 2014-10-27 | 510-361 | 0–9 XXXall 10 · 6 holders which blocks → | LEVEL 3 TELECOM OF CALIFORNIA, LP - CA | 7718 | HAYWARD | CA |
| — | 510-227 | 0XXX1XXX2XXX4XXX5XXX6XXX7XXX8XXX9XXX · 6 holders which blocks → | LEVEL 3 TELECOM OF CALIFORNIA, LP - CA | 7718 | OKLD ALMD | CA |
| — | 510-240 | 0XXX1XXX2XXX4XXX5XXX6XXX7XXX8XXX9XXX · 8 holders which blocks → | LEVEL 3 TELECOM OF CALIFORNIA, LP - CA | 7718 | FRNK GRNLF | CA |
| — | 510-253 | 0XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 3 holders which blocks → | LEVEL 3 TELECOM OF CALIFORNIA, LP - CA | 7718 | RICHMOND | CA |
| — | 510-379 | 0XXX4XXX5XXX6XXX7XXX8XXX9XXX · 3 holders which blocks → | LEVEL 3 TELECOM OF CALIFORNIA, LP - CA | 7718 | OKLD MN-PD | CA |
| — | 510-467 | 0XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 3 holders which blocks → | LEVEL 3 TELECOM OF CALIFORNIA, LP - CA | 7718 | OKLD FRTVL | CA |
| — | 510-725 | 0XXX1XXX2XXX4XXX5XXX6XXX7XXX8XXX9XXX · 4 holders which blocks → | LEVEL 3 TELECOM OF CALIFORNIA, LP - CA | 7718 | OKLD BKLY | CA |
| — | 510-943 | 0XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX9XXX · 3 holders which blocks → | LEVEL 3 TELECOM OF CALIFORNIA, LP - CA | 7718 | FRNK MAIN | CA |
| — | 510-969 | 0XXX2XXX4XXX5XXX6XXX7XXX8XXX9XXX · 2 holders which blocks → | LEVEL 3 TELECOM OF CALIFORNIA, LP - CA | 7718 | 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.