13. If the six-digit number $a 2016 b$ is divisible by 12, then the number of such six-digit numbers is $\qquad$.
【Analysis】First, based on the fact that a number divisible by 12 must also be divisible by 4 and 3, find the last digits that can be divided by 4, and then determine if the sum of the digits is a multiple of 3 to solve the problem.

【Solution】Solution: To determine if a number can be divided by 4, check if the last two digits can be divided by 4. That is, the last two digits are
(1) 60, when $2+0+1+6+0=9, \therefore a$ can be 3, 6, 9, a total of 3 values.
(2) 64, when $2+0+1+6+4=13, \therefore a$ can be 2, 5, 8, a total of 3 values.
(3) 68, when $2+0+1+6+8=17, \therefore a$ can be 1, 4, 7, a total of 3 values.

Therefore, the answer is: 9 values