lets us suppose we have to make DFA of whose integer equivalent is divisible by x
then write the x in the form of $2^{k}*m$ where m is odd no
then the minimum no of state in the DFA will be k+m
now we will understand it by using examples
ex1 divisible by 16
then write 16 in form of $2^{k}*m$ ( $2^{4}*1$) so 4+1=5 answer
ex2 divisible by 12
then write 12 in form of $2^{k}*m$ ( $2^{2}*3$) so 2+3=5 answer
ex3 divisible by 18
then write 18 in form of $2^{k}*m$ ( $2^{1}*9$) so 1+9=10 answer