The number 821,100 can be evenly divided by 1 2 3 4 5 6 7 10 12 14 15 17 20 21 23 25 28 30 34 35 42 46 50 51 60 68 69 70 75 84 85 92 100 102 105 115 119 138 140 150 161 170 175 204 210 230 238 255 276 300 322 340 345 350 357 391 420 425 460 476 483 510 525 575 595 644 690 700 714 782 805 850 966 1,020 1,050 1,150 1,173 1,190 1,275 1,380 1,428 1,564 1,610 1,700 1,725 1,785 1,932 1,955 2,100 2,300 2,346 2,380 2,415 2,550 2,737 2,975 3,220 3,450 3,570 3,910 4,025 4,692 4,830 5,100 5,474 5,865 5,950 6,900 7,140 7,820 8,050 8,211 8,925 9,660 9,775 10,948 11,730 11,900 12,075 13,685 16,100 16,422 17,850 19,550 23,460 24,150 27,370 29,325 32,844 35,700 39,100 41,055 48,300 54,740 58,650 68,425 82,110 117,300 136,850 164,220 205,275 273,700 410,550 and 821,100, with no remainder.
Since 821,100 cannot be divided by just 1 and 821,100, it is a composite number.