Question

h/2pi is not an integer, then how can angular momentum be an integral multilple of h/2pi

Answer 1

"Integral multiple" means that the number multiplied by h/2pi must be an integer. It does not mean that the product of the multiplication must be an integer (and in fact it's never an integer). It's saying that acceptable angular momentums can be:
h/2pi , h/pi, 3h/2pi, 2h/pi, 5h/2pi, 3h/pi, 7h/2pi, ...