Yes, COSMOPOLITAN is a Scrabble word!

Letter values in Scrabble US: C 3, O 1, S 1, M 3, O 1, P 3, O 1, L 1, I 1, T 1, A 1, N 1.

Is it a valid word?

COSMOPOLITAN is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

growing or occurring in many parts of the world
composed of people from or at home in many parts of the world; especially not provincial in attitudes or interests
of worldwide scope or applicability

Also: widely distributed, world-wide.