The Soviet Union existed from 1922 to 1991, 69 years.
About 75 years, from its formation to its dissolution.
27 December 1979 - 15 February 1989 .
Fifteen independent democratic nations. Namely,RussiaBelarusUkraineLithuaniaLatviaEstoniaMoldovaArmeniaAzerbijianGeorgiaUzbekistanTurkemistanKazakstanKyrgistanTajikistan
Mikhail Gorbachev was the last leader of the Soviet Union.