11. Among the positive integers $1,2, \cdots, 20210418$, how many numbers have a digit sum of 8?
The number of digits whose sum is 8 and does not exceed 7 digits is $C_{14}^{6}$, which is the number of non-negative integer solutions to the equation $x_{1}+x_{2}+\cdots+x_{7}=8$, such as $|\bigcirc| O O|O \bigcirc||\bigcirc 0| \bigcirc$ representing 122021; The number of 8-digit numbers whose first digit is 1 and the sum of the digits is 8 is $C_{13}^{6}$; The number of 8-digit numbers whose first 3 digits are 200 and the sum of the digits is 8 is $C_{10}^{4}$; The number of 8-digit numbers whose first 3 digits are 201 and the sum of the digits is 8 is $C_{9}^{4}$; The number of 8-digit numbers whose first 4 digits are 2020 and the sum of the digits is 8 is $C_{7}^{3}$; The number of 8-digit numbers whose first 5 digits are 20210 and the sum of the digits is 8 is $C_{5}^{2}$. Therefore, the total number of numbers that meet the criteria is $C_{14}^{6}+C_{13}^{6}+C_{10}^{4}+C_{9}^{4}+C_{7}^{3}+C_{5}^{2}=5100$.