A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2870400 can be evenly divided by 1 2 3 4 5 6 8 10 12 13 15 16 20 23 24 25 26 30 32 39 40 46 48 50 52 60 64 65 69 75 78 80 92 96 100 104 115 120 128 130 138 150 156 160 184 192 195 200 208 230 240 260 276 299 300 312 320 325 345 368 384 390 400 416 460 480 520 552 575 598 600 624 640 650 690 736 780 800 832 897 920 960 975 1,040 1,104 1,150 1,196 1,200 1,248 1,300 1,380 1,472 1,495 1,560 1,600 1,664 1,725 1,794 1,840 1,920 1,950 2,080 2,208 2,300 2,392 2,400 2,496 2,600 2,760 2,944 2,990 3,120 3,200 3,450 3,588 3,680 3,900 4,160 4,416 4,485 4,600 4,784 4,800 4,992 5,200 5,520 5,980 6,240 6,900 7,176 7,360 7,475 7,800 8,320 8,832 8,970 9,200 9,568 9,600 10,400 11,040 11,960 12,480 13,800 14,352 14,720 14,950 15,600 17,940 18,400 19,136 20,800 22,080 22,425 23,920 24,960 27,600 28,704 29,900 31,200 35,880 36,800 38,272 41,600 44,160 44,850 47,840 55,200 57,408 59,800 62,400 71,760 73,600 89,700 95,680 110,400 114,816 119,600 124,800 143,520 179,400 191,360 220,800 239,200 287,040 358,800 478,400 574,080 717,600 956,800 1,435,200 and 2,870,400, with no remainder.
Since 2,870,400 cannot be divided by just 1 and 2,870,400, it is not a prime number.