Prefix 303-434 — Denver, CO

NANPA CO code assignment, current as of July 28, 2026.

Area code
303
Prefix (NXX)
434
Rate center
Denver
State
Colorado
Time zone
Mountain
Code holder
T-MOBILE USA, INC.
OCN
6529
Pooled
Yes (thousands-block pooling)
LATA
656

A phone number starting 303-434 was issued in the Denver rate center of CO — part of area code 303.

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.

A scammer can display 303-434 without ever touching CO. When in doubt, end the call and reach the company or agency through its official website; unwanted robocalls belong in the FTC's fraud report queue.

Denver is part of the Denver-Aurora-Centennial, CO Metropolitan Statistical Area. For routing purposes it sits in LATA 656. Numbers here keep Mountain time.

Neighboring prefixes

Prefixes adjacent to 303-434
PrefixRate centerCode holder
303-431 Denver QWEST CORPORATION
303-432 Denver QWEST CORPORATION
303-433 Denver QWEST CORPORATION
303-435 Denver T-MOBILE USA, INC.
303-436 Denver QWEST CORPORATION
303-437 Denver T-MOBILE USA, INC.

FAQ

Where is 303-434 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 303-434 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 303-434 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.