The sum of the positive divisors of a positive integer of the form 2^i*3^j is equal to 1815. What is i+j?
2^i*3^j ==2^3 * 3^4 =648
648 =(1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 27, 36, 54, 72, 81, 108, 162, 216, 324, 648) >>Total = 1815
