add zeros in front in excel code example

Example 1: excel set n number of digits in cell or column

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

Example 2: excel complete with 0

=TEXT(A2,"00000000000")

or format only with 
	CTRL+1 > Number > Custom > Type > 00000000000