How do you write 3.5 trillion in numbers?

Answer 1

3.5 * 10^12

That is correct if you use the short scale (as used in places like USA); I use the long scale (as used in places like Europe), and so I write it:

3.5 x 1018 (= 3,500,000,000,000,000,000)

Answer 2

3500000000000

Answer 3

3500000000000