A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1562400 can be evenly divided by 1 2 3 4 5 6 7 8 9 10 12 14 15 16 18 20 21 24 25 28 30 31 32 35 36 40 42 45 48 50 56 60 62 63 70 72 75 80 84 90 93 96 100 105 112 120 124 126 140 144 150 155 160 168 175 180 186 200 210 217 224 225 240 248 252 279 280 288 300 310 315 336 350 360 372 400 420 434 450 465 480 496 504 525 558 560 600 620 630 651 672 700 720 744 775 800 840 868 900 930 992 1,008 1,050 1,085 1,116 1,120 1,200 1,240 1,260 1,302 1,395 1,400 1,440 1,488 1,550 1,575 1,680 1,736 1,800 1,860 1,953 2,016 2,100 2,170 2,232 2,325 2,400 2,480 2,520 2,604 2,790 2,800 2,976 3,100 3,150 3,255 3,360 3,472 3,600 3,720 3,906 4,200 4,340 4,464 4,650 4,960 5,040 5,208 5,425 5,580 5,600 6,200 6,300 6,510 6,944 6,975 7,200 7,440 7,812 8,400 8,680 8,928 9,300 9,765 10,080 10,416 10,850 11,160 12,400 12,600 13,020 13,950 14,880 15,624 16,275 16,800 17,360 18,600 19,530 20,832 21,700 22,320 24,800 25,200 26,040 27,900 31,248 32,550 34,720 37,200 39,060 43,400 44,640 48,825 50,400 52,080 55,800 62,496 65,100 74,400 78,120 86,800 97,650 104,160 111,600 130,200 156,240 173,600 195,300 223,200 260,400 312,480 390,600 520,800 781,200 and 1,562,400, with no remainder.
Since 1,562,400 cannot be divided by just 1 and 1,562,400, it is not a prime number.