Daniel Tammet sees numbers, and to him eleven is friendly

Daniel Tammet is a British writer who, in 2004, recited pi from memory to 22,514 decimal places in front of an audience at Oxford’s Museum of the History of Science. It took him five hours and nine minutes. He is autistic and has synaesthesia: in his mind numbers are not symbols but shapes, colours, textures and moods. He sees prime numbers as “smooth and round shapes, similar to pebbles on a beach”, and can recognise every one up to 9,973 by its “pebble-like” quality.

In his memoir Born on a Blue Day (2006) he introduces a few of them:

“Eleven is friendly and five is loud, whereas four is both shy and quiet – it’s my favourite number, perhaps because it reminds me of myself.”

Four is his favourite, then. But eleven, a prime and so one of his round pebbles, is friendly, and that is a good word for it.