Answer
$10,400,600$
Work Step by Step
Recall:
$C(n, r)=\dfrac{n!}{(n-r)!r!}$
Thus.
\begin{align*}
\require{cancel}
C(26, 13)&=\dfrac{26!}{(26-13)!13!}\\
\\
&=\dfrac{26!}{13!13!}\\
\end{align*}
Using a calculator gives
$C(26, 13)=\frac{26!}{13!(26-13)!}=10,400,600$
