Find the difference between the greatest and the least $5$-digit number that can be written using the digits $6,2,7,4,3$ each only once.

Greatest number$=76432$
Smallest number$=23467$
Difference$=76432-23467$
$76432$
$-23467$
___________
$52965$
___________
Therefore, the difference between the greatest and the least number that can be written using the digits $6,2,7,4,3$ each only once is $52,965$.