The telephone code of Cuba is 53.

To make a call to Cuba from Russia, you first need to dial "8", wait for a dial tone, then dial "10" - for an international call, and after that the phone code of Cuba is 53.

After that you will need the city code and phone number itself. For example, in Havana code 7, so to call there, you will need to type:

8-ring-10-53-7-phone number.

For other country codes of Cuba see here.