When you enter numbers in Excel, there are a few things to keep in mind. First, make sure that your cells are formatted as "Number" or "Currency." Otherwise, your numbers will be treated as text, and you'll run into problems with calculations. Second, if you're using a comma as a decimal separator (as is common in many European countries), you'll need to change the decimal separator in Excel's settings. Otherwise, your commas will be ignored. Finally, remember that you can always use the "Text to Columns" feature if you need to split up numbers that are entered as text.
To format cells as "Number" or "Currency," select the cells that you want to format and then click the "Home" tab. In the "Number" group, there are two buttons for number formats - one for "Number" and one for "Currency." Choose the appropriate button depending on what format you want. If you want to use commas as decimal separators, click the "Additional Settings" button after selecting the "Number" button. In the Format Cells dialog box that appears, select the "Use 1000 Separator (,) checkbox under the Decimal places section.
If you have numbers entered as text, you can use the "Text to Columns" feature to split them up into separate columns. This is useful if, for example, you have a column of data that includes both first and last names, and you want to split them up into two separate columns. To use this feature, select the column of data that you want to split up and then click the Data tab. In the Data Tools group, there is a button for "Text to Columns." Click this button and then follow the instructions in the wizard that appears.