3

3 is the only Integer which is the sum of the preceding Positive Integers ($1+2=3$) and the only number which is the sum of the Factorials of the preceding Positive Integers ($1!+2!=3$). It is also the first Odd Prime. A quantity taken to the Power 3 is said to be Cubed.

See also 1, 2, 3x+1 Mapping, Cubed, Period Three Theorem, Super-3 Number, Ternary, Three-Colorable, Zero