11. Among the 10-digit positive integers in decimal notation that only contain the digits 0 and $\mathrm{I}$, the number of those divisible by 11 is
$\qquad$ .
11. 126
$$
S=\sum_{k=1}^{5} C_{5}^{*} C_{4}^{*-1}=C_{5}^{1} C_{4}^{0}+C_{5}^{2} C_{4}^{1}+C_{5}^{3} C_{4}^{2}+C_{5}^{4} C_{4}^{3}+C_{5}^{5} C_{4}^{4}=126 .
$$