The number 3,280,320 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 15 16 17 18 20 24 30 32 34 36 40 45 48 51 60 64 67 68 72 80 85 90 96 102 120 134 136 144 153 160 170 180 192 201 204 240 255 268 272 288 306 320 335 340 360 402 408 480 510 536 544 576 603 612 670 680 720 765 804 816 960 1,005 1,020 1,072 1,088 1,139 1,206 1,224 1,340 1,360 1,440 1,530 1,608 1,632 2,010 2,040 2,144 2,278 2,412 2,448 2,680 2,720 2,880 3,015 3,060 3,216 3,264 3,417 4,020 4,080 4,288 4,556 4,824 4,896 5,360 5,440 5,695 6,030 6,120 6,432 6,834 8,040 8,160 9,112 9,648 9,792 10,251 10,720 11,390 12,060 12,240 12,864 13,668 16,080 16,320 17,085 18,224 19,296 20,502 21,440 22,780 24,120 24,480 27,336 32,160 34,170 36,448 38,592 41,004 45,560 48,240 48,960 51,255 54,672 64,320 68,340 72,896 82,008 91,120 96,480 102,510 109,344 136,680 164,016 182,240 192,960 205,020 218,688 273,360 328,032 364,480 410,040 546,720 656,064 820,080 1,093,440 1,640,160 and 3,280,320, with no remainder.
Since 3,280,320 cannot be divided by just 1 and 3,280,320, it is a composite number.