I assume the answer to my question is pretty simple but I fail to find it.

In a sheet there are 3 “main” columns (A to C) with the data I enter and 3 “helper” columns (D to F) consisting of formulas (REGEX functions) modifying the contents of the main columns (necessary for the desired sorting).

Now I usually enter the formula in D2, E2 and F2 (the first row is a column label), and once they prove to work correctly, I copy and drag these cells down the sheet a bit. Often 1,000 cells down a column are enough, but sometimes I need up to 10,000 cells.

Is there an easy way to automatically fill the cells with the formula down to D1048576, E1048576, and F1048576?

And, if I later I need to change the formula in D2, how can I easily update the formula in all the cells down to D1048576?