The number 1,386,840 can be evenly divided by 1 2 3 4 5 6 7 8 10 12 13 14 15 20 21 24 26 28 30 35 39 40 42 52 56 60 65 70 78 84 91 104 105 120 127 130 140 156 168 182 195 210 254 260 273 280 312 364 381 390 420 455 508 520 546 635 728 762 780 840 889 910 1,016 1,092 1,270 1,365 1,524 1,560 1,651 1,778 1,820 1,905 2,184 2,540 2,667 2,730 3,048 3,302 3,556 3,640 3,810 4,445 4,953 5,080 5,334 5,460 6,604 7,112 7,620 8,255 8,890 9,906 10,668 10,920 11,557 13,208 13,335 15,240 16,510 17,780 19,812 21,336 23,114 24,765 26,670 33,020 34,671 35,560 39,624 46,228 49,530 53,340 57,785 66,040 69,342 92,456 99,060 106,680 115,570 138,684 173,355 198,120 231,140 277,368 346,710 462,280 693,420 and 1,386,840, with no remainder.
Since 1,386,840 cannot be divided by just 1 and 1,386,840, it is a composite number.