The answer is 42 !! AFTER pondering the weighty question of the mass of the Milky Way galaxy, astronomers have come up with an answer: 42.
That is, our galaxy weighs three times 10 to the power of 42kg – a number written as 3 followed by 42 zeroes, which has echoes of author Douglas Adams’s fictional answer to the question of life, the universe and everything in his series Hitchhiker’s Guide to the Galaxy.

More here