Telephone numbers in Russia are under a unified numbering plan with Kazakhstan, both of which share the international code +7. Historically, +7 was used as the country calling code for all of the Soviet Union. Following the Soviet break-up, all of its former republics, save for Russia and Kazakhstan, switched to new country codes. Following Abkhazia's secession from Georgia, Abkhazia switched to the Russian telephone codes +7 840 for landlines and +7 940 for mobile phones, though it still can be reached via the Georgian telephone code +995 44.
Following the annexation of Crimea by Russia in 2014, the Republic of Crimea switched to the Russian telephone codes +7 978 for mobile phones and +7 365 for landlines, while the city of Sevastopol switched to the codes +7 978 for mobile phones and +7 869 for landlines, since 7 May 2015.