A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 850200 can be evenly divided by 1 2 3 4 5 6 8 10 12 13 15 20 24 25 26 30 39 40 50 52 60 65 75 78 100 104 109 120 130 150 156 195 200 218 260 300 312 325 327 390 436 520 545 600 650 654 780 872 975 1,090 1,300 1,308 1,417 1,560 1,635 1,950 2,180 2,600 2,616 2,725 2,834 3,270 3,900 4,251 4,360 5,450 5,668 6,540 7,085 7,800 8,175 8,502 10,900 11,336 13,080 14,170 16,350 17,004 21,255 21,800 28,340 32,700 34,008 35,425 42,510 56,680 65,400 70,850 85,020 106,275 141,700 170,040 212,550 283,400 425,100 and 850,200, with no remainder.
Since 850,200 cannot be divided by just 1 and 850,200, it is not a prime number.