The number 321,300 can be evenly divided by 1 2 3 4 5 6 7 9 10 12 14 15 17 18 20 21 25 27 28 30 34 35 36 42 45 50 51 54 60 63 68 70 75 84 85 90 100 102 105 108 119 126 135 140 150 153 170 175 180 189 204 210 225 238 252 255 270 300 306 315 340 350 357 378 420 425 450 459 476 510 525 540 595 612 630 675 700 714 756 765 850 900 918 945 1,020 1,050 1,071 1,190 1,260 1,275 1,350 1,428 1,530 1,575 1,700 1,785 1,836 1,890 2,100 2,142 2,295 2,380 2,550 2,700 2,975 3,060 3,150 3,213 3,570 3,780 3,825 4,284 4,590 4,725 5,100 5,355 5,950 6,300 6,426 7,140 7,650 8,925 9,180 9,450 10,710 11,475 11,900 12,852 15,300 16,065 17,850 18,900 21,420 22,950 26,775 32,130 35,700 45,900 53,550 64,260 80,325 107,100 160,650 and 321,300, with no remainder.
Since 321,300 cannot be divided by just 1 and 321,300, it is a composite number.