Find the missing number $1,12,144,\dots ,20736$.

The given series follows a geometric progression where each term is multiplied by $12$:
* First term: $1$
* Second term: $1\times 12=12$
* Third term: $12\times 12=144$
* Fourth term (missing): $144\times 12=1728$
* Fifth term: $1728\times 12=20736$
Therefore, the missing number is $1728$.