I'm guessing Athena is the central character. There could be other characters such as a mentor figure who guides Athena in understanding and using her intelligence better. And maybe there are some ordinary people in the story who are affected by Athena's actions and intelligence, and they play important roles in the overall plot.
Since I haven't read it, I can't say for sure. But Athena is likely to be a main character, given the title. There may also be characters who are her friends or foes, like perhaps a sidekick who helps her in her adventures or an enemy who wants to stop her from using her brain power.
The main character is probably Athena. There might be a group of scientists or scholars who are either in awe of Athena's brain or are competing with her. There could also be a family member or a close acquaintance who has a special bond with Athena and helps her in times of need, or causes some conflict in her life because of their relationship.