6,000,000,015
15,000,000,000
15,000,000,000
15,000,027
It is 0.000000015
15,140,607,000
15,000,000,000,000.One billion is 1 with 9 zeroes or 1,000,000,000.So 15000 billion is 15,000,000,000,000 or simply 15 trillion.
1,500,000,000= 1.5 X 109========
15
15/100000000 or 0.00000015 or 1.5 * 10^-7
15 billion is correct unless there is some reason to capitalize the word billion, perhaps in a title.
one thousand million=15 billion 1 billion/ 15 billion = 1/15= 0.0666
15