The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 3285.7097\\[1 em]x_2 &= -9.3548+247.7643i\\[1 em]x_3 &= -9.3548-247.7643i \end{aligned} $$Polynomial $ 8x^3-26136x^2+x-1615903005 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.