How a number with +370 is written
International format: +370 6XX XXXXX
National format: (0-6XX) XXXXX
Inside Lithuania a number starts with the trunk prefix 0; drop it after +370.
Mobile number length: 8 digits after +370
Calling a Lithuania number from abroad
From another country, dial + (or your exit code: 00 in most of the world, 011 from North America), then 370, then the national number without its trunk prefix.