$$\lim_{x \to 0^-}\left(x \sqrt[4]{\operatorname{atan}{\left(6 x \right)}}\right) = 0$$
More at x→0 from the left$$\lim_{x \to 0^+}\left(x \sqrt[4]{\operatorname{atan}{\left(6 x \right)}}\right) = 0$$
$$\lim_{x \to \infty}\left(x \sqrt[4]{\operatorname{atan}{\left(6 x \right)}}\right) = \infty$$
More at x→oo$$\lim_{x \to 1^-}\left(x \sqrt[4]{\operatorname{atan}{\left(6 x \right)}}\right) = \sqrt[4]{\operatorname{atan}{\left(6 \right)}}$$
More at x→1 from the left$$\lim_{x \to 1^+}\left(x \sqrt[4]{\operatorname{atan}{\left(6 x \right)}}\right) = \sqrt[4]{\operatorname{atan}{\left(6 \right)}}$$
More at x→1 from the right$$\lim_{x \to -\infty}\left(x \sqrt[4]{\operatorname{atan}{\left(6 x \right)}}\right) = - \infty \sqrt[4]{-1}$$
More at x→-oo