Working with numbers that begin with 0

I have a column on an Excel spreadsheet in which I need to show a 6-digit number, many of which begin with as many as 4 "0's". When I format the column as a number, enter the number with the preceding "0's", the zeroes are dropped. I need to show the number, exactly as entered....with the zeroes in place. Can someone suggest a solution for this issue. Thank you.