A six-sided polygon is a hexagon, one of the three regular polygons capable of tiling the plane. A hexagon also has 6 edges as well as 6 internal and external angles. 6 is the second smallest composite number. It is also the first number that is the sum of its proper divisors, making it the smallest perfect number. It is also the only perfect number that doesn't have a digital root of 1. 6 is the first unitary perfect number, since it is the sum of its positive proper unitary divisors, without including itself. Only five such numbers are known to exist.6 is the largest of the four all-Harshad numbers. 6 is the 2nd superior highly composite number,[6] the 2nd colossally abundant number,the 3rd triangular number,the 4th highly composite number, a pronic number, a congruent number, a harmonic divisor number,and a semiprime. 6 is also the first Granville number, or S {\displaystyle {\mathcal {S}}}-perfect number. A Golomb ruler of length 6 is a "perfect ruler".
