8

Definition
$8$ (eight) is:


 * The $2$nd cube number after $1$:
 * $8 = 2^3$


 * The $6$th Fibonacci number:
 * $1, 1, 2, 3, 5, 8, \ldots$


 * The $2$nd octagonal number after $1$:
 * $1, 8, 21, 40, \ldots$


 * The $6$th Ulam number after $1, 2, 3, 4, 6$:
 * $8 = 2 + 6$


 * Equal to the sum of the digits of its cube:
 * $8^3 = 512$, while $5 + 1 + 2 = 8$


 * The $4$th almost perfect number after $1, 2, 4$:
 * $\sigma \left({8}\right) = 15 = 2 \times 8 - 1$


 * The base of the octal number system.

Also see

 * Cube which is One Less than a Square
 * Cubic Fibonacci Numbers
 * Positive Integers Equal to Sum of Digits of Cube


 * Eight Convex Deltahedra


 * Definition:Octal Numbers