A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6385680 can be evenly divided by 1 2 3 4 5 6 7 8 9 10 12 14 15 16 18 20 21 24 28 30 35 36 40 42 45 48 49 56 60 63 70 72 80 84 90 98 105 112 120 126 140 144 147 168 180 181 196 210 240 245 252 280 294 315 336 360 362 392 420 441 490 504 543 560 588 630 720 724 735 784 840 882 905 980 1,008 1,086 1,176 1,260 1,267 1,448 1,470 1,629 1,680 1,764 1,810 1,960 2,172 2,205 2,352 2,520 2,534 2,715 2,896 2,940 3,258 3,528 3,620 3,801 3,920 4,344 4,410 5,040 5,068 5,430 5,880 6,335 6,516 7,056 7,240 7,602 8,145 8,688 8,820 8,869 10,136 10,860 11,403 11,760 12,670 13,032 14,480 15,204 16,290 17,640 17,738 19,005 20,272 21,720 22,806 25,340 26,064 26,607 30,408 32,580 35,280 35,476 38,010 43,440 44,345 45,612 50,680 53,214 57,015 60,816 65,160 70,952 76,020 79,821 88,690 91,224 101,360 106,428 114,030 130,320 133,035 141,904 152,040 159,642 177,380 182,448 212,856 228,060 266,070 304,080 319,284 354,760 399,105 425,712 456,120 532,140 638,568 709,520 798,210 912,240 1,064,280 1,277,136 1,596,420 2,128,560 3,192,840 and 6,385,680, with no remainder.
Since 6,385,680 cannot be divided by just 1 and 6,385,680, it is not a prime number.