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