To write 4.26 billion in numerical form, you express it as 4,260,000,000. This is done by placing the decimal, 4.26, in the billions place and adding the appropriate number of zeros to reach the billions mark. Therefore, 4.26 billion equals 4.26 followed by nine zeros.
0.0005
As a number: 7,125,000,000 = 7.125 billion
As a number it is: 24,600,000,000 = 24.6 billion
19.35 billion = 19,350,000,000
As a number it is: 1,800,000,000 = 1.8 billion
0.0005
Since you asked how I would write the number, the answer is 1031.
19.35 billion = 19,350,000,000
As a number: 7,125,000,000 = 7.125 billion
As a number it is 12,800,000,000 = 12.8 billion
As a number it is: 6,080,000,000 = 6.08 billion
As a number it is: 24,600,000,000 = 24.6 billion
As a number it is: 529,600,000,000 = 529.6 billion
As a number it is: 1,800,000,000 = 1.8 billion
As number it is: 1,500,000,000
.426 = 426/1000 = 213/500
80 billion = 80,000,000,000