A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 5285250 can be evenly divided by 1 2 3 5 6 9 10 15 18 25 27 29 30 45 50 54 58 75 81 87 90 125 135 145 150 162 174 225 243 250 261 270 290 375 405 435 450 486 522 675 725 729 750 783 810 870 1,125 1,215 1,305 1,350 1,450 1,458 1,566 2,025 2,175 2,250 2,349 2,430 2,610 3,375 3,625 3,645 3,915 4,050 4,350 4,698 6,075 6,525 6,750 7,047 7,250 7,290 7,830 10,125 10,875 11,745 12,150 13,050 14,094 18,225 19,575 20,250 21,141 21,750 23,490 30,375 32,625 35,235 36,450 39,150 42,282 58,725 60,750 65,250 70,470 91,125 97,875 105,705 117,450 176,175 182,250 195,750 211,410 293,625 352,350 528,525 587,250 880,875 1,057,050 1,761,750 2,642,625 and 5,285,250, with no remainder.
Since 5,285,250 cannot be divided by just 1 and 5,285,250, it is not a prime number.