The answer depends how you read this question.
1) What country is to the east of Russia? -- There is no country on Russia's Eastern border since Russia extends from the northwest corner of Asia all the way to the northeast corner of Asia. It could be noted, however, that if someone traveled due east from the Asian-Russian city of Vladivostok, they would arrive in Japan, but as Japan is an archipelago, Russia has no current land borders with Japan. It could also be noted that there are some Russia-Kazakhstan, Russia-Mongolia, and Russia-China borders where Russia is on the Western side and the other country is on the Eastern side, but all of these borders are primarily north-south and Russia continues to the East of all of these countries.
A final small note, the Russian province of Kalingrad, which is physically unconnected to mainland Russia does have an eastern land border which is occupied entirely by Lithuania.
2) What country has an eastern border upon which Russia rests? -- From North to South: Norway, Finland, Estonia, Latvia, Belarus, and Ukraine. There are a number of other countries that share a West-East border with Russia, but their primary border with Russia is North-South and Russia also exists further west of these countries.
Mongolia, China and almost North Korea.
North Korea and Russia do in fact share a boarder in the far southeast of Russia.
Russia.
The landlocked country that borders China to the south and Russia to the north is Mongolia. The capital of Mongolia is Ulan Bator.
Mongolia
Mongolia?
Ulaanbaatar, Mongolia
The only country which borders both Russia and India is China.
The country is Mongolia and its capital is Ulan Bator.
The country is Mongolia and its capital is Ulan Bator.
Russia borders 11 countries
China is the only country that borders both Russia and India.
Russia is the country that borders Finland on the east. Russia is the largest country in land mass in the world. It covers one eighth of the Earth.
Ulan Bator is the capital of Mongolia. It is located south of Russia and north of China.