The number 1,518,660 can be evenly divided by 1 2 3 4 5 6 9 10 11 12 13 15 18 20 22 26 30 33 36 39 44 45 52 55 59 60 65 66 78 90 99 110 117 118 130 132 143 156 165 177 180 195 198 220 234 236 260 286 295 330 354 390 396 429 468 495 531 572 585 590 649 660 708 715 767 780 858 885 990 1,062 1,170 1,180 1,287 1,298 1,430 1,534 1,716 1,770 1,947 1,980 2,124 2,145 2,301 2,340 2,574 2,596 2,655 2,860 3,068 3,245 3,540 3,835 3,894 4,290 4,602 5,148 5,310 5,841 6,435 6,490 6,903 7,670 7,788 8,437 8,580 9,204 9,735 10,620 11,505 11,682 12,870 12,980 13,806 15,340 16,874 19,470 23,010 23,364 25,311 25,740 27,612 29,205 33,748 34,515 38,940 42,185 46,020 50,622 58,410 69,030 75,933 84,370 101,244 116,820 126,555 138,060 151,866 168,740 253,110 303,732 379,665 506,220 759,330 and 1,518,660, with no remainder.
Since 1,518,660 cannot be divided by just 1 and 1,518,660, it is a composite number.