Country code +7 was originally the entire USSR. Following the breakup of the USSR, most of the republics got their own separate country codes. As of 2012, country code +7 is used by Russia and Kazakhstan.
Numbers beginning with +7 7 are in Kazakhstan (including landlines and mobiles).
Numbers beginning with +7 3 or +7 4, plus some numbers beginning with +7 8 are landlines in Russia.
Numbers beginning with +7 9 are mobiles in Russia, plus premium numbers.
Numbers beginning with +7 0, +7 1, +7 2, and +7 5 are invalid.
The disputed region of Abkhazia uses numbers in +7 840 (landlines) and +7 940 (mobiles), as well as numbers in Georgia's country code +995.
(The plus sign means "insert your international access prefix here." From a GSM mobile phone, you can enter the number in full international format, starting with the plus sign. The most common prefix is 00, but North America (USA, Canada, etc.) uses 011, Japan uses 010, Australia uses 0011, and many other countries use different prefixes.)
7 is the country code of Kazakhstan/Russia
invalid code Telephone country code +7 is Russia and Kazakhstan, but there are no valid numbers beginning with +7 0.
Telephone country codes never begin with zero, and there is no country code +77. Country code +7 is Russia and Kazakhstan, and a number beginning with +7 7xx is in Kazakhstan. See the related question for more information.
Country code +7 was originally the entire USSR. When the USSR dissolved, all of the other newly independent constituent republics got their own telephone country codes, leaving only Russia and Kazakhstan. There has been speculation that Kazakhstan may at some point split into its own separate country code, but for now the economic benefits of being more closely associated with Russia, plus the costs of changing the telephone numbering system, outweigh the benefits of having a separate code.
Russia and Kazakhstan both have country code +7.
Kazakhstan shares country code +7 with Russia. Numbers in Kazakhstan begin with +7 7.
+7 is Russia and Kazakhstan.
Canada is an international call from the United States because Canada is a different country. Likewise, even though Russia and Kazakhstan share telephone country code +7, a call from Russia to Kazakhstan or vice-versa is still an international call, because it is a call from one country to a different country.
Country code +7 is Russia and Kazakhstan. Numbers beginning with +7 76 are in Kazakhstan.
Country code +7 is Russia and Kazakhstan, but +7 27 is an invalid code.
+7 is shared by Russia and Kazakhstan.
Telephone country codes have 1 to 3 digits. Country code +1 is North America (USA, Canada, etc.). Country code +7 is Russia and Kazakhstan. All other country codes are 2 or 3 digits.