In scientific notation, we write a number so that it has single digit to the left of decimal sign and is multiplied by an integer power of 10.
Note that moving decimal p digits to right is equivalent to multiplying by 10^p and moving decimal q digits to left is equivalent to dividing by 10^q.
Hence, we should either divide the number by 10^p i.e. multiply by 10^(-p) (if moving decimal to right) or multiply the number by 10^q (if moving decimal to left).
In other words, it is written as axx10^n, where 1<=a<10 and n is an integer.
To write 5,100,000 in scientific notation, we will have to move the decimal point six points to left, which literally means dividing by 10^6.
Hence in scientific notation 5,100,000=5.1xx10^6 (note that as we have moved decimal six points to left, we are multiplying by 10^6 to compensate for division by 10^6.
