021 is: · in Iran, the telephone area code for the city of Tehran. This code became popularized by Tehrani rapper Hich Kas. · in South Africa, the area code for the city of Cape Town. · in Ireland, the area code for the city of Cork and a surrounding part of County Cork. · in the United Kingdom, the former area code for Birmingham England (changed to 0121 on 16 April 1995). · in New Zealand, the "area code" for cellular phones on the Vodafone network.