Mystery number

I am a mystery number
between one and ninety nine;
in fact, I have two digits,
and I am not a prime.
When you add me to the number
of spots upon two dice,
divide me by eleven
and add on two score (twice),
subtract a baker's dozen,
times the days within one week,
minus days in a leap year,
it just adds to the mystique.
Halve your current total,
then subtract three score and ten;
if the answer's quite unlucky,
what is MY name then?