What is 1000000000000000000000000000000000000000 number called?

It's called "ten to the thirty-ninth power".

It's equal to (one googol) divided by (ten to the forty-first power).

It's also equal to (the square root of one googol) divided by (one billion).

It's also roughly the number of seconds in 7,041,797,000,000,000,000,000 times

the present age of the Earth.