As a number it is: 61,000,000,000
I write 620 billion as 620 billion.
Sixteen point two billion is how I would write it.
You write 3.56 billion as 3,560,000,000.
4.3571
61% = 0.61
40,300,000,000
It is: 61 = LXI
61 = sixty one
As a number it is: 1,800,000,000 = 1.8 billion
Since you asked how I would write the number, the answer is 1031.
0.0197
1,000 billion billion is: 1,000,000,000,000,000,000,000