6 * 10^9. 6 is the first number, 9 is the number of zeroes that come after, but that only works with simple numbers like this.
For the more general case, take the number 57,000.
The first number in standard form has to be between 1 and 10 (but not including 10) and include all the non-zero numbers, so in this case it would be 5.7. The other number is the number of digits after the first digit (i.e. the total number of digits - 1), so here it would be 4. So the answer would be 5.7 * 10^4.
