\[\boxed{\mathbf{1558}\mathbf{.}}\]
\[f(x) = \cos{4x};\ F\left( \frac{\pi}{24} \right) = - 1:\]
\[F(x) = \frac{1}{4}\sin{4x} + C.\]
\[- 1 = \frac{1}{4} \bullet \sin\left( 4 \bullet \frac{\pi}{24} \right) + C\]
\[- 1 = \frac{1}{4} \bullet \sin\frac{\pi}{6} + C\]
\[- 1 = \frac{1}{4} \bullet \frac{1}{2} + C\]
\[- 1 = \frac{1}{8} + C\]
\[C = - 1 - \frac{1}{8} = - \frac{9}{8}.\]
\[Искомая\ первообразная:\]
\[F(x) = \frac{1}{4}\sin{4x} - \frac{9}{8} =\]
\[= \frac{1}{8}\left( 2\sin{4x} - 9 \right).\]
\[Ответ:\ \ F(x) = \frac{1}{8}\left( 2\sin{4x} - 9 \right).\]