Adding a letter at the end of each number in a column using CONCATENATE function in Excel

1. Insert a new column next to the column with the numbers you want to add a letter to.
2. In the first cell of the new column, type in the formula
   Formula:

   =CONCATENATE(A1,"X") 

   where "A1" is the cell reference of the first cell in the original column and "X" is the letter you want to add at the end of each number.
3. Press Enter to apply the formula to the first cell.
4. Double-click the bottom right corner of the cell to autofill the formula down the entire column.

This will add the letter "X" (or any other letter you choose) at the end of each number in the original column. You can then copy and paste the values in the new column over the original column to replace the numbers with the new values that include the letter at the end.