Explanation

The prime factorization of 72 involves dividing it by its smallest prime factor repeatedly:

1. $72 div 2 = 36$
   
2. $36 div 2 = 18$
   
3. $18 div 2 = 9$
   
4. $9 div 3 = 3$
   
5. $3 div 3 = 1$
   

So, $72=2^3\times 3^2$