Prefix 313-221 — Detroit Zone 01, MI

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

Numbers in the 313-221 prefix are registered to the Detroit Zone 01 rate center in MI, inside area code 313. The prefix is the second block of a ten-digit US number (313-221-XXXX) and pins the number to a billing locality.

The assigned code holder is MICHIGAN BELL TEL CO, operating company number 9323, assigned June 17, 2005. 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 Detroit-Warren-Dearborn, MI Metropolitan Statistical Area. The serving LATA is 340. Local time follows the Eastern zone.

Spoofing means this prefix on your screen doesn't guarantee a Detroit Zone 01 caller. Verify independently before trusting a request for money or data.

Neighboring prefixes

FAQ

Where is 313-221 located?

The prefix is assigned to the Detroit Zone 01 rate center in MI, area code 313. It is part of the Detroit-Warren-Dearborn, MI Metropolitan Statistical Area.

Which company owns 313-221 numbers?

MICHIGAN BELL TEL 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 313-221 safe to answer?

The prefix itself says nothing about the caller. Legitimate Detroit Zone 01 businesses and spoofed robocalls can both display it. Never share personal data with an unverified inbound caller.