Prefix 303-406 — Denver, CO
Numbers in the 303-406 prefix are registered to the Denver rate center in CO, inside area code 303. The prefix is the second block of a ten-digit US number (303-406-XXXX) and pins the number to a billing locality.
NANPA's central-office code records list LEVEL 3 COMMUNICATIONS, LLC - CO (OCN 6118) as the code holder. Because 303-406 participates in thousands-block pooling, individual 1,000-number blocks may belong to other carriers than the code holder.
The rate center lies in the Denver-Aurora-Centennial, CO Metropolitan Statistical Area. The serving LATA is 656. Local time follows the Mountain zone.
Spoofing means this prefix on your screen doesn't guarantee a Denver caller. Verify independently before trusting a request for money or data.
Neighboring prefixes
| Prefix | Rate center | Code holder |
|---|---|---|
| 303-403 | Denver | QWEST CORPORATION |
| 303-404 | Denver | QWEST CORPORATION |
| 303-405 | Denver | QWEST CORPORATION |
| 303-407 | Denver | ONVOY, LLC - CO |
| 303-408 | Denver | NEW CINGULAR WIRELESS PCS, LLC |
| 303-409 | Denver | LEVEL 3 COMMUNICATIONS, LLC - CO |
FAQ
Where is 303-406 located?
The prefix is assigned to the Denver rate center in CO, area code 303. It is part of the Denver-Aurora-Centennial, CO Metropolitan Statistical Area.
Which company owns 303-406 numbers?
LEVEL 3 COMMUNICATIONS, LLC - CO holds the code, but the prefix is pooled — individual thousands-blocks can be assigned to other carriers, and numbers may be ported to any provider.
Is a call from 303-406 safe to answer?
The prefix itself says nothing about the caller. Legitimate Denver businesses and spoofed robocalls can both display it. Never share personal data with an unverified inbound caller.