6

6 (six) is the natural number following 5 and preceding 7. The SI prefix for 1000 is exa (E), and for its reciprocal atto (a). Six is the second smallest composite number, its proper divisors being 1, 2 and 3. Since six equals the sum of these proper divisors, six is the smallest perfect number. As a perfect number, 6 is related to the Mersenne prime 3, since 2(2 - 1) = 6. (The next perfect number is 28.) It is the only even perfect number that i... more

6 (six) is the natural number following 5 and preceding 7. The SI prefix for 1000 is exa (E), and for its reciprocal atto (a). Six is the second smallest composite number, its proper divisors being 1, 2 and 3. Since six equals the sum of these proper divisors, six is the smallest perfect number. As a perfect number, 6 is related to the Mersenne prime 3, since 2(2 - 1) = 6. (The next perfect number is 28.) It is the only even perfect number that is not the sum of successive odd cubes. Being perfect six is the root of the 6-aliquot tree, and is itself the aliquot sum of only one number; the square number, 25. Unrelated to 6 being a perfect number, a Golomb ruler of length 6 is a "perfect ruler." Six is a congruent number. Six is the first discrete biprime (2.3) and the first member of the (2.q) discrete biprime family. Six is the only number that is both the sum and the product of three consecutive positive numbers. Six is a unitary perfect number, a harmonic divisor number and a highly... less