8649 students were sitting in a lecture room

Let number of students in each row of the lecture room be $x$. Then, number of rows $=x$

$\therefore$ Total students $=x \times x=x^{2}$

According to the question,

$x^{2}=8649$

$\Rightarrow \quad x=\sqrt{8649}$

$\therefore \quad x=93$

Hence, there are 93 students in each row of the lecture room.