A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1100550 can be evenly divided by 1 2 3 5 6 10 11 15 22 23 25 29 30 33 46 50 55 58 66 69 75 87 110 115 138 145 150 165 174 230 253 275 290 319 330 345 435 506 550 575 638 667 690 725 759 825 870 957 1,150 1,265 1,334 1,450 1,518 1,595 1,650 1,725 1,914 2,001 2,175 2,530 3,190 3,335 3,450 3,795 4,002 4,350 4,785 6,325 6,670 7,337 7,590 7,975 9,570 10,005 12,650 14,674 15,950 16,675 18,975 20,010 22,011 23,925 33,350 36,685 37,950 44,022 47,850 50,025 73,370 100,050 110,055 183,425 220,110 366,850 550,275 and 1,100,550, with no remainder.
Since 1,100,550 cannot be divided by just 1 and 1,100,550, it is not a prime number.