When large numbers have many different decimals in them, such as 642 500 000 000, naming them with scientific notation is about the same, but with one difference. Still counting the number of numbers after the first number (in this case, after the 6 there are 11 numbers) you need to include the ones that are not zero in the formula, but after a decimal point. So 642 500 000 000 will be 6.425 x 10. When naming by grouping, each group of the name of the group. With the same number, it would be said to be 642 billion, 500 million (US) or 642 milliard, 500 million (Eur).