Christopher is the appealing and sympathetic autistic teenager who is the protagonist and tells us the story from his point of view. Because of the first person narrative, it is his character that dominates the novel as we see everything through his eyes. What is stressed throughout the novel is the way that Christopher finds the adult world so hard to comprehend and understand. Note how he links prime numbers and life in the following quote:
Prime numbers are what is left when you have taken all the patterns away. I think prime numbers are like life. They are very logical but you could never work out the rules, even if you spent all your time thinking about them.
Throughout the novel, Haddon creates a contrast between Christopher's character, who, by his own admission, does not "tell lies" and sees everything incredibly literally, and the world of deceit and lies in which adults exist. Christopher as a character strictly doesn't "change," as he remains incapable of lying and unable to understand the interactions of those around him, but the narrative mode creates a juxtaposition between Christopher and the often petty disagreements of adults. The character of Christopher therefore emphasises the way in which adults are often more childish than children themselves, which is a key theme of this novel.