NUMBER NINE

 Number NINE

Number Nine is a peculiar and interesting number which is attributed different

names in mathematics literature.Moreover it is a number which is equally valued

 by all religions and  numerology,astrology, as well.

9 is natural number lying between numbers 8 and 10 It is the highest single 

digit number in the base 10 system .This is a composite number its divisors 

being 1 and 3 .  3 x 3  is 9 and so the third square number. It is the first

 composite number and first composite odd number and also single digit 

composite odd number. A polygon of 9 sides is called nonagon or 

ennaegon. Group of nine of anything is called ennead.

If any natural number is multiplied by 9, then its  digital sum is always nine. 

This method of finding  digital sum and casting out nines is a quick way 

of testing calculations of sums,differences,multiplications,divisions.

This is known ever since 12th century. 

When you multiply 12345679 by 9 you get 111111111

12345679x 81 =999999999 

123456789 x 999999999 = 12345678887654321 

123456789 ÷ 999999999 = 0.123456789123456789123……