Los Angeles County, California.
The closest communities in those area codes would be Glendale in area code 818 (and overlay area code 747) to Pico Rivera in area code 562. As the crow flies, that's about 20 km. At the farthest, it's about 70 km from the northwest of 818/747 to the southeast of 562.
Area code 818 and overlay area code 747 serve the San Fernando Valley area of greater Los Angeles, California, including Glendale, Burbank, San Fernando, Canoga Park, Sherman Oaks, Agoura Hills, La Cañada Flintridge, and Calabasas.(Note that area code boundaries in California do not exactly follow city or county boundaries.)
Montrose, California, is in area code 818 and overlay code 747.
The 818 area code was created in 1984, it covers the San Fernando Valley of Los Angeles. The major city within the area code is Van Nuys, but it also has limited use within Hollywood, Los Angeles and Burbank.
Area code 818 (exchange 753) CA - Agoura, Arleta, Burbank, Calabasas, Canoga Par
The Mission Hills, California, is in area code 818, with overlay area code 747. Any existing 818 numbers will remain in area code 818 for the rest of eternity, or until we move to four-digit area codes, probably some time mid-21st century. However, new numbers may be assigned in the 747 overlay code, or in subsequent overlay codes that may be added in the future.
Burbank, California, is in area code 818, with overlay code 747.
Toluca Lake is served by area code 818 and overlay code 747.
Toluca Lake is located in area code 818 and overlay area code 747.
The country code and area code of Dazhou- SC, China is 86, (0)818.
The country code and area code of Arkhangelsk region, Russian Federation is 7, (8)818.
Until some time in the 1980's, all of Los Angeles was area code 213. Area code 818 split off, with the area that is now 818, 747, and 626. Then area code 310 split off, with the area that is now area codes 310, 424, and 562. When area codes were originally assigned in 1947, area code 213 included not only all of Los Angeles, but also Bakersfield, San Diego, San Luis Obispo, Palm Springs, and about the southern 1/3 of California.