Why 13 number is unlucky in india?

That’s an interesting one. It’s actually a bit of a misconception. The number 13 isn't traditionally considered unlucky in India at all. That whole superstition is a purely Western concept, linked to Christian beliefs like the Last Supper.

The idea most likely trickled into Indian urban culture during the British era and through modern global media. In traditional Indian numerology and astrology (Jyotish), other numbers hold far more significance, with the number 8, for instance, often being seen as a challenging one. So, it's really more of a borrowed belief than a homegrown Indian superstition.