Is the following number Prime or Composite? 9999997777 7755555533 3333111111 . Notice the descending order of the odd numbers grouped in strings of fives!. Thanks for any help.

Guest Apr 15, 2017

#1**+1 **

Very interesting and clever, whoever came up with it!!.

However, using a primality test shows that it is a composite number and factors as follows:

999999 777777 555555 333333 111111 = 3 x 7 x 11 x 13 x 37 x 9000007000005000003000001.

P.S. Notice that it is grouped in "sixes" not "fives". Also, notice that all its factors are odd!.

Guest Apr 15, 2017