Excel 에서 설정한 번호의 자리에서 열

N

Right click on the column-> format cells -> number -> custom. 
Choose the 0 type and put n zeros in the entry box (for n numbers).
click okay. All numbers entered will be n digits.

example :  type: 00000
all number will have 5 digits :  00004, 03452,00876,45627 etc