Nine or 9

Nine is the largest single digit number in the Arabic, or Base 10, system of numbers.  It is the integer that is greater than 8 yet less than 10.

9 = (3)(3) = 3² = 1 + 3 + 5 

9 = 1001 in the Base 2 system of numbers. 

The square root of Nine is Three.

Nine is the Sum of the first 3 odd numbers

Nine squared is 81. 

There were Nine Muses.

There are said to have been Nine original members of the Knights Templar. 

Nine woods are to be used in a Wiccan Bonfire.

Three groups of Three Knocks, or Nine knocks, are required to become a Master Mason.