Prefix 303-356 — Denver, CO
Numbers in the 303-356 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 (303-356-XXXX) and pins the number to a billing locality.
The assigned code holder is T-MOBILE USA, INC., operating company number 6529. This is a pooled prefix — expect numbers within it to be split across more than one carrier in 1,000-number blocks.
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 |
|---|---|---|
| 303-353 | Denver | COMCAST IP PHONE, LLC |
| 303-354 | Denver | TELEPORT COMMUNICATIONS AMERICA, LLC - CO |
| 303-355 | Denver | QWEST CORPORATION |
| 303-357 | Denver | MCIMETRO ACCESS TRANSMISSION SERVICES LLC |
| 303-358 | Denver | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - CO |
| 303-359 | Denver | T-MOBILE USA, INC. |
FAQ
Where is 303-356 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 303-356 numbers?
T-MOBILE USA, INC. 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 303-356 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.