Is 64a^2 - 144ap + 81p^2 a perfect square trinomial, and how do you factor it?

$64 {a}^{2} = {\left(8 a\right)}^{2}$ and $81 {p}^{2} = {\left(9 p\right)}^{2}$ or ${\left(- 9 p\right)}^{2}$
${\left(8 a - 9 p\right)}^{2}$ which does indeed work...
${\left(8 a - 9 p\right)}^{2} = {\left(8 a\right)}^{2} - 2 \left(8 a\right) \left(9 p\right) + {\left(9 p\right)}^{2}$
$= 64 {a}^{2} - 144 a p + 9 {p}^{2}$