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.

Either format the cells as Text and then enter the numbers, or enter the numbers with a leading apostrophe(e.g., '012345), or custom format as 000000

U can also do this,

Right click the column in which u r entering the number.
Select Format Cell.
Select the last option custom.

On the right side u can see a box (under Type)
Enter --- @
in that box and click ook