Pardon me for saying this. I do not attach any luck to numbers. True enough. Luck has been associated with numbers throughout the human civilisation in all parts of the world at all times. It is nevertheless a superstition.
I was thinking that 13 is my lucky number, when I was little it used to 7 but then I realized that when ever I used 7 no luck happened and since then 13 was mine. For no reason at all but just 13.
As I said before, I do not attach any luck or ill luck to numbers. But in the western countries, there has been a traditional superstition that 13 in an unlucky number.