Prime numbers...

... are divisible only by 1 and by themselves. They stand in their place in the infinite series of natural numbers, squashed in between two others, like all other numbers, but a step further on than the rest. They are suspicious and solitary, which is why Mattia thought they were wonderful. Sometimes he thought that they had ended up in that sequence by mistake, that they’d been trapped like pearls strung on a necklace. At other times he suspected that they too would rather have been like all the others, just ordinary numbers, but for some reason they weren’t capable of it. The second thought struck him mostly at night, in the chaotic interweaving of images that comes before sleep, when the mind is too weak to tell itself lies.
In his first-year Mattia had studied the fact that among the prime numbers there are some that are even more special. Mathematicians call them twin primes: they are pairs of prime numbers that are close to one another, almost neighbours, but between them there is always an even number that prevents them from really touching. Numbers like 11 and 13, like 17 and 19, 41 and 43. If you have the patience to go on counting, you discover that these pairs gradually become rarer. You encounter increasingly isolated primes, lost in that silent, measured space made only of numbers and you become aware of the distressing sense that the pairs encountered up until that point were an accidental fact, that their true fate is to remain alone. Then, just when you’re about to surrender, when you no longer have any desire to go on counting, you come across another two twins, clutching one another tightly. Among mathematicians it is a common conviction that however far you go, there will always be more pairs, even if no one can say where, until they are discovered.

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A big *thanks* to the person who sent me a surprise package, including a book by Paolo Giorgano, The Solitude of Prime Numbers, where the above extract comes from.