The Solitude of Prime Numbers (original: La solitudine dei numeri primi) is a novel by Italian writer Paolo Giordano, published in 2008. It also won the 2008 Strega Prize. A film version of the novel, with minor adaptations and directed by Saverio Costanzo, was released in 2010.
The novel narrates the childhood and young adult life of a boy, Mattia, and a girl, Alice, both of whom had exposure to traumatic situations when they were both 8 years old. Alice bears the physical scars of a terrible skiing accident which nearly killed her. Mattia bears the emotional scars of having lost his disabled twin sister, after leaving her alone in a park in order to attend the birthday party of a friend. These traumas manifest themselves again physically later in both of their lives, with Alice being anorexic, and Mattia cutting himself. At school, both are outsiders, much as prime numbers are outsiders from the other numbers. Both lonely, they befriend each other, forming a special relationship — very close but never romantic. The relationship is compared to Prime pairs: always together, but never touching.
When the gifted Mattia wins a mathematics posting that takes him thousands of miles away, their relationship appears to have run its course. But when Alice sights a woman who could be Mattia’s sister, the two are brought back together again. Though they clearly love each other, they are unable to express their emotions.