A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 4201560 can be evenly divided by 1 2 3 4 5 6 8 9 10 11 12 15 18 20 22 24 30 33 36 40 44 45 55 60 66 72 88 90 99 110 120 132 165 180 198 220 264 330 360 396 440 495 660 792 990 1,061 1,320 1,980 2,122 3,183 3,960 4,244 5,305 6,366 8,488 9,549 10,610 11,671 12,732 15,915 19,098 21,220 23,342 25,464 31,830 35,013 38,196 42,440 46,684 47,745 58,355 63,660 70,026 76,392 93,368 95,490 105,039 116,710 127,320 140,052 175,065 190,980 210,078 233,420 280,104 350,130 381,960 420,156 466,840 525,195 700,260 840,312 1,050,390 1,400,520 2,100,780 and 4,201,560, with no remainder.
Since 4,201,560 cannot be divided by just 1 and 4,201,560, it is not a prime number.