You can add a zero before a number in Google Sheets and Excel using this tutorial. You need to change cell formatting or use function.

The most obvious way to increment a number in Excel is to add a value to it. Start with any value in cell A1, and enter "=A1+1" in cell A2 to increment the starting value by one. Copy the formula ...

You can sum a series of numbers in Microsoft Excel manually by typing in a simple formula, or automatically with a tool.