Barstow is in area code 760, with overlay code 442.
I assume you mean Barstow, CA and not Barstow, TX. The Approx. driving time from Flagstaff, AZ to Barstow, CA is about 5.5 hours, if you take I-40.
Bartow, Florida, is in area code 863. Bartow, Georgia, is in area code 478.Barstow, California, is in area code 760 and overlay code 442.
760, there's a website for it - Area-Codes.com
Martinez, CA, is in area code 925.
According to the sign on I-40 in Wilmington, NC, it is 2,554 miles to Barstow, CA.
Victorville, CA, is in area code 760 and overlay code 442.