15 million = 15,000,000 (6 zeros before decimal)
There are six zeros in a million, so you would just need to add six zeros to 15 to get 15,000,000. You can also move the decimal point over six places to the right to get the same answer.
15 zeroes: 1,000,000,000,000,000
A quadrillion has 15 zeros, so there would be 15 zeros in a quadrillion miles.
6
To get around the confusion between the US and European use of billion (thousand million or million million) and higher numbers new names, based on Greek roots, were proposed. In many countries the European names have now been dropped in favour of the US names. Pentillion was the name proposed for quadrillion = 1015 It would have had 15 zeros if the name had caught on.
15 million = 15,000,000
One million trillion billion googolplex =10,000,000,000,000,000,000,000,000,00010100 but the progression is: thousand - 3 zeros million - 6 zeros billion 9 zeros trillion - 12 zeros quadrillion - 15 zeros quintillion - 18 zeros etc, googleplex - an inconceiveably large number equal to ten times the amount of a number that would be 10 with a hundred 0's behind it, or 100,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000
15 zeros
18 zeros 1 million = 6 zeros 1 billion = 9 1 trillion = 12 1 quadrillion = 15 1 quintillion = 18 1 sextillion =21
15 zeros
There are 15 zeros in a quadrillion. 1,000,000,000,000,000