A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2728500 can be evenly divided by 1 2 3 4 5 6 10 12 15 17 20 25 30 34 50 51 60 68 75 85 100 102 107 125 150 170 204 214 250 255 300 321 340 375 425 428 500 510 535 642 750 850 1,020 1,070 1,275 1,284 1,500 1,605 1,700 1,819 2,125 2,140 2,550 2,675 3,210 3,638 4,250 5,100 5,350 5,457 6,375 6,420 7,276 8,025 8,500 9,095 10,700 10,914 12,750 13,375 16,050 18,190 21,828 25,500 26,750 27,285 32,100 36,380 40,125 45,475 53,500 54,570 80,250 90,950 109,140 136,425 160,500 181,900 227,375 272,850 454,750 545,700 682,125 909,500 1,364,250 and 2,728,500, with no remainder.
Since 2,728,500 cannot be divided by just 1 and 2,728,500, it is not a prime number.