The charge for one electron = 1.60 x 10^-19. the formula for one coulomb = 1/ (1.60 x 10^-19)
Looking for the reason why dividing the charge of one electron into 1
A coulomb is defined as the charge of 6.24x10^18 electrons.
To find the charge on a single electron, we take the inverse of this number : 1/(6.24x10^18) = 1.6x10^-19.
To get back to coulomb's from the electron charge, we take 1/(1.6x10^-19) = 6.24x10^18 and we are back to the number we started with.
Taking the inverse of a number twice in a row (1/1/x) always gives you the number you started with.
Think of it this way: If we divide a pie into 8 slices, each slice is 1/8th of a pie.
If we know that each slice is 1/8th, to find out how many slices are in a pie we calculate 1/(1/8) = 8.
Same thing with couloumbs and electrons.