The Devil's Arithmetic begins with Hannah and her mother and then quickly introduces Hannah's brother and father as well. Hannah's mother is concerned with the preservation of their Jewish traditions, as is Hannah's father; Hannah's little brother, Aaron, is nervous about the role he must play in the Seder. Hannah is entitled and self-absorbed, not wanting to participate or even remember her own family's history and traditions or the people who were lost in the Holocaust. She grows and changes throughout the story after being transported into the past and to Poland.
Once in 1942, Hannah takes on the identity of Chaya, one of her relatives. As Chaya, she experiences the Holocaust firsthand, and through her ordeal, she finds her own inner strength. During her incarceration in a Nazi concentration camp, she relies on her talent for storytelling to comfort herself and others. She learns the meaning of loss and self-sacrifice and experiences the suffering of her family members, so when she reemerges into her own time at the close of the novel, she has an in-depth understanding of the past.
Rivka, a young girl Chaya meets in the camp, is strong and tough. The evening Chaya meets her, Rivka gives a speech:
I play the man's game. I play the Devil's game. I play God's game. And so I stay alive. Alive I can help you. Dead I am no help to you at all.
Rivka has lost six out of eight members of her family, and yet she takes strength from her survival. Even though she is young, she has wisdom beyond her years, and it is her tutelage that provides the groundwork for Chaya’s survival in the camp.
Shmuel, Chaya's uncle, enters the narrative by describing himself:
I have all my teeth and all my hair, two fine workhorses, a four-room house, and twenty acres of land beside. I work hard and I do not smell all that bad.
Shmuel is lighthearted and brave and provides a bit of levity in what becomes a very dark story. He is also faithful in his devotion to his family and his undying love of Fayge, his fiancée.
As the daughter of a rabbi, Fayge is entitled, and she wants nothing more than to be happily married to Shmuel. The fact that she is more concerned over her wedding dress and her spoiled wedding than she is over the threat of death shows her initially shallow character. She remains static throughout the novel and does not grow or change—she is only focused on being with Shmuel and goes to her death by flinging herself at his feet during his execution.
Gitl, Shmuel's sister, is hard-nosed and fierce in her love of family and her desire to survive. She is a fighter through and through. She is one of the only survivors of the camp, and her survival is mainly due to her tenacity and a bit of good luck.