15. After converting the fraction $\frac{123456789}{2^{26} \times 5^{4}}$ into a decimal, there are ( ) digits after the decimal point.
(A) 4
(B) 22
(C) 26
(D) 30
(E) 104
15. C.

Notice,
$$
\begin{array}{l}
\frac{123456789}{2^{26} \times 5^{4}}=\frac{123456789}{2^{22} \times 10^{4}} \\
=\frac{12345.6789}{2^{22}}<1 .
\end{array}
$$

Since the last digit after the decimal point in the numerator of the fraction is odd, each division by 2 will add one more digit after the decimal point. Therefore, 22 more digits are added after the decimal point. Combining this with the original 4 digits after the decimal point in the numerator, the result is 26.