A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6381480 can be evenly divided by 1 2 3 4 5 6 7 8 10 12 14 15 20 21 24 28 30 35 40 42 56 60 70 71 84 105 107 120 140 142 168 210 213 214 280 284 321 355 420 426 428 497 535 568 642 710 749 840 852 856 994 1,065 1,070 1,284 1,420 1,491 1,498 1,605 1,704 1,988 2,130 2,140 2,247 2,485 2,568 2,840 2,982 2,996 3,210 3,745 3,976 4,260 4,280 4,494 4,970 5,964 5,992 6,420 7,455 7,490 7,597 8,520 8,988 9,940 11,235 11,928 12,840 14,910 14,980 15,194 17,976 19,880 22,470 22,791 29,820 29,960 30,388 37,985 44,940 45,582 53,179 59,640 60,776 75,970 89,880 91,164 106,358 113,955 151,940 159,537 182,328 212,716 227,910 265,895 303,880 319,074 425,432 455,820 531,790 638,148 797,685 911,640 1,063,580 1,276,296 1,595,370 2,127,160 3,190,740 and 6,381,480, with no remainder.
Since 6,381,480 cannot be divided by just 1 and 6,381,480, it is not a prime number.