# 6

#### In quantum computing, a qubit or quantum bit (sometimes qbit) is the basic unit of quantum information: 6

6 (six) is the natural number following 5 and preceding 7. It is a composite number and the smallest perfect number.

6 is the smallest positive integer which is neither a square number nor a prime number. Six is the second smallest composite number; its proper divisors are 1, 2 and 3.

Since six equals the sum of its proper divisors, six is the smallest perfect number, Granville number, and {\displaystyle {\mathcal {S}}}{\mathcal {S}}-perfect number.

As a perfect number:

6 is related to the Mersenne prime 3, since 21(22 – 1) = 6. (The next perfect number is 28.)
6 is the only even perfect number that is not the sum of successive odd cubes.
6 is the root of the 6-aliquot tree, and is itself the aliquot sum of only one number; the square number, 25.
Six is the only number that is both the sum and the product of three consecutive positive numbers.

The evolution of our modern digit 6 appears rather simple when compared with the other digits. The modern 6 can be traced back to the Brahmi numerals of India, which are first known from the Edicts of Ashoka circa 250 BCE. It was written in one stroke like a cursive lowercase e rotated 90 degrees clockwise. Gradually, the upper part of the stroke (above the central squiggle) became more curved, while the lower part of the stroke (below the central squiggle) became straighter. The Arabs dropped the part of the stroke below the squiggle. From there, the European evolution to our modern 6 was very straightforward, aside from a flirtation with a glyph that looked more like an uppercase G.

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https://en.m.wikipedia.org/wiki/6