A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1000800 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 15 16 18 20 24 25 30 32 36 40 45 48 50 60 72 75 80 90 96 100 120 139 144 150 160 180 200 225 240 278 288 300 360 400 417 450 480 556 600 695 720 800 834 900 1,112 1,200 1,251 1,390 1,440 1,668 1,800 2,085 2,224 2,400 2,502 2,780 3,336 3,475 3,600 4,170 4,448 5,004 5,560 6,255 6,672 6,950 7,200 8,340 10,008 10,425 11,120 12,510 13,344 13,900 16,680 20,016 20,850 22,240 25,020 27,800 31,275 33,360 40,032 41,700 50,040 55,600 62,550 66,720 83,400 100,080 111,200 125,100 166,800 200,160 250,200 333,600 500,400 and 1,000,800, with no remainder.
Since 1,000,800 cannot be divided by just 1 and 1,000,800, it is not a prime number.