4. In a chess tournament, there are $n$ female players and $9 n$ male players. Each player plays one game against each of the other $10 n-1$ players. The scoring system is as follows: the winner gets 2 points, the loser gets 0 points, and in the case of a draw, each player gets 1 point. After the tournament, it was found that the total score of all male players is 4 times the total score of all female players. Then, all possible values of $n$ are $\qquad$
4.1.

Let the total score of the girls be $m$. Then the total score of the boys is $4 m$. According to the problem,
$$
\begin{array}{l}
\frac{10 n(10 n-1)}{2} \times 2=5 m \\
\Rightarrow m=2 n(10 n-1) .
\end{array}
$$

Since each player competes in $10 n-1$ matches, the maximum score is $2(10 n-1)$, so the total score of the girls
$$
m \leqslant 2 n(10 n-1) \text {. }
$$

Therefore, each girl must win all her matches.
Thus, $n=1$.