NumberResearchRecent prefix assignments
0 prefixes assigned in the last 30 days · from the daily NANPA CO code file, 09/21/2026
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 |
|---|---|---|---|---|---|---|
| 2021-03-24 | 831-266 | 0–9 XXXall 10 · 6 holders which blocks → | T-MOBILE USA, INC. | 6529 | SANTA CRUZ | CA |
| 2014-09-23 | 831-346 | 0–9 XXXall 10 · 5 holders which blocks → | T-MOBILE USA, INC. | 6529 | SANTA CRUZ | CA |
| 2002-01-16 | 831-210 | 6XXX7XXX · 2 holders which blocks → | T-MOBILE USA, INC. | 6529 | SALINAS | CA |
| 2001-12-14 | 831-295 | 1XXX4XXX5XXX6XXX7XXX8XXX · 3 holders which blocks → | T-MOBILE USA, INC. | 6529 | SANTA CRUZ | CA |
| 2001-12-14 | 831-297 | 1XXX4XXX5XXX6XXX7XXX8XXX9XXX · 3 holders which blocks → | T-MOBILE USA, INC. | 6529 | HOLLISTER | CA |
| 2001-12-14 | 831-406 | 1XXX2XXX3XXX4XXX5XXX6XXX7XXX8XXX · 5 holders which blocks → | T-MOBILE USA, INC. | 6529 | WATSONVL | CA |
| 2001-09-12 | 831-207 | 0XXX1XXX2XXX4XXX5XXX6XXX7XXX8XXX · 3 holders which blocks → | T-MOBILE USA, INC. | 6529 | HOLLISTER | CA |
| — | 831-224 | 1XXX8XXX · 2 holders which blocks → | T-MOBILE USA, INC. | 6529 | MONTEREY | CA |
| — | 831-240 | 0–9 XXXall 10 · 5 holders which blocks → | T-MOBILE USA, INC. | 6529 | SALINAS | CA |
| — | 831-512 | 0–9 XXXall 10 · 3 holders which blocks → | T-MOBILE USA, INC. | 6529 | SALINAS | CA |
| — | 831-539 | 0XXX2XXX4XXX5XXX7XXX8XXX · 3 holders which blocks → | T-MOBILE USA, INC. | 6529 | WATSONVL | CA |
| — | 831-750 | 1XXX3XXX · 2 holders which blocks → | T-MOBILE USA, INC. | 6529 | WATSONVL | CA |
| — | 831-970 | none assigned yet which blocks → | T-MOBILE USA, INC. | 6529 | SALINAS | CA |
Source: NANPA CO Code Assignments (Utilized, All States, Public), file date 09/21/2026 — Tier A primary source, refreshed on every import. Viewing is free; bulk downloads require a membership.