144 million native speakers, 250 million total speakers. Official language of Russia and many of the countries in the former Soviet Union, and 1 of the 6 official languages of the United Nations.
A quick google will give you plenty of reasons to learn Russian so here are some of my favourites;
1. You are an ambitious traveller and Russia is the next stop on your travel list.
2. Russia is a regional power and is returning as a world power by speaking Russian, you can engage in the Russian economy.
3. Your government needs more Russian-language specialists.
4.You are passionate about Russian classical literature and dream to read the works of Russian classics in the original.
5. English Is Not A Fallback : only 5.5% of the Russian population claiming English as a first or second language.
6. The best way to understand a culture is through its language.