5% is equal to 5/100, so on a calculator, you would multiply 8,648,459 * 0.05. An easy way to calculate 5% of any number using mental math is to first calculate 10% of that number, then divide 10% in half, or by 2, which will equal 5% of the original number. 10% is easy to calculate because you move the decimal place one spot to the left. For example:

8,648,459 * 10% (or 0.10) = 864,845.9

864,845.9/2 = 432,422.95

432,422.95 = 5% of 8,648,459

Ok, so that one wasn't so easy to do mentally. An easier example:

What is 5% of 37?

10%*37 = 3.7

3.7/2 = 1.85

1.85 = 5% of 37

8,648,459 * 10% (or 0.10) = 864,845.9

864,845.9/2 = 432,422.95

432,422.95 = 5% of 8,648,459

Ok, so that one wasn't so easy to do mentally. An easier example:

What is 5% of 37?

10%*37 = 3.7

3.7/2 = 1.85

1.85 = 5% of 37