Taking the square root of a number is such a common mathematical operation, that the spot on the root sign where the index would normally be written for cubic and other roots, may simply be left blank for square roots, as it is tacitly understood. The square root of 2 was the first known irrational number. The smallest field has two elements. In a set-theoretical construction of the natural numbers, 2 is identified with the set {{∅},∅}. This latter set is important in category theory: it is a subobject classifier in the category of sets. Two consecutive twos (as in "22" for "two twos"), or equivalently "2-2", is the only fixed point of John Conways look-and-say function. This in contrast, for example, with "1211", which would read as "one 1, one 2, and two 1s" or "111221".
Oculocerebrorenal syndrome (also called Lowe syndrome) is a rare X-linked recessive disorder characterized by congenital cataracts, hypotonia, intellectual disability, proximal tubular acidosis, aminoaciduria and low-molecular-weight proteinuria. Lowe syndrome can be considered a cause of Fanconi syndrome (bicarbonaturia, renal tubular acidosis, potassium loss and sodium loss). Signs and symptoms
Boys with Lowe syndrome are born with cataracts in both eyes; glaucoma is present in about half of the individuals with Lowe syndrome, though usually not at birth. While not present at birth, kidney problems develop in many affected boys at about one year of age. Renal pathology is characterized by an abnormal loss of certain substances into the urine, including bicarbonate, sodium, potassium, amino acids, organic acids, albumin, calcium and L-carnitine. This problem is known as Fanconi-type renal tubular dysfunction. Genetics
This syndrome is caused by mutations in the OCRL gene which encodes an inositol polyphosphate-5-phosphatase. At least one mechanism by which these mutations cause this syndrome is by loss of its Rab-binding domain.This protein is associated with the primary cilia of the retinal pigment epithelial cells, fibroblasts and kidney tubular cells. This suggests that this syndrome is due to dysfunction of the cilia in these cells.