Prefix Information
The prefix 991 is part of area code 406 serving Billings, Montana.
This exchange contains 10,000 possible phone numbers (406-991-0000 through 406-991-9999).
Phone numbers with prefix 991 in area code 406. Location: Billings, Montana.
The prefix 991 is part of area code 406 serving Billings, Montana.
This exchange contains 10,000 possible phone numbers (406-991-0000 through 406-991-9999).