Unlucky Thirteen

 Unlucky Thirteen

Is Thirteen Really unlucky???
I really don't know; but...I have seen some interesting facts about thirteen (13).
    Thirteen is a number of surprise from ancient age .It is not only a number of surprise ;many times it is considered as a number of 'bad luck'.
     It is also said that, monks had difficulty writing the calendar of any year with 13 full moon.It is difficult to adjust 13 months in a year.Mean while a century has 37 years with 13 full moon and 63 years with 12 full moon!!!
      In ancient cultures , 13 represents feminity; because it corresponded to the number of menstrual cycles in a year(13×12=364 days).
    In this world there are many such things or events which surprises us about 13.But we have seen the magical properties of 13 in the world of mathematics.
    In mathematics 13 is the sixth prime.It's Roman equivalent is XIII.
     Binary:11012, Ternary: 1113, Quoternary:314, Quinary:235, sensory:216, octal:158, Duodecimal:1112, Hexadecimal:D16; vigesimal :D20.
These are the mathematical identity of 13.
      Here are some interesting facts about 13...
           6×6+13=49
           6×66+13=409
           6×666+13=4009
           6×6666+13=40009
 
                8×8+13=77
                8×88+13=717
                8×888+13=7117
                8×8888+13=71117
               
                      9×9+13=94
                      9×99+13=904
                      9×999+13=9004
                      9×9999+13=90004
          Is not surprising???
     Also the sum of the primes from 2 to 13 is 41, which is the 13 th prime number. Again,13 is the sum of two consecutive squares of 2 and 3!!!
     13 is the smallest emrip(a prime number whose digital reversal forms a different prime number); here it is noted that the reverse of 13 is 31 ; which is also prime number.A standard deck cards has four suits and 13 denominators, for a total 13×4=52 cards.
     A 24 hours clock uses the number 13 in the form of 13:00- 13:59, to represent the14th hour of cycle.
      Such surprising and intersting properties are endless...
      At the end, I think mathematically 13 is equal interesting as other numbers.It's not unlucky! It,s magical!!!

  

 If you find out any incorrect information or know anything more about this , please write it in the comment section!