Number of four-digit positive integers if the product of their digits is divisible by 3 is. 

Total number of 4 digited

$\text{ + ve integer }=9\times {10}^3$

$\text{ Product will be divisible by }3\text{ , if atleast one digit is }0\text{ or }3\text{ or }6\text{ or }9$

$\therefore \mathrm{an}\text{s}=9\times {10}^3-6^4=7704$