A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6628980 can be evenly divided by 1 2 3 4 5 6 10 12 15 17 20 30 34 51 60 67 68 85 97 102 134 170 194 201 204 255 268 291 335 340 388 402 485 510 582 670 804 970 1,005 1,020 1,139 1,164 1,340 1,455 1,649 1,940 2,010 2,278 2,910 3,298 3,417 4,020 4,556 4,947 5,695 5,820 6,499 6,596 6,834 8,245 9,894 11,390 12,998 13,668 16,490 17,085 19,497 19,788 22,780 24,735 25,996 32,495 32,980 34,170 38,994 49,470 64,990 68,340 77,988 97,485 98,940 110,483 129,980 194,970 220,966 331,449 389,940 441,932 552,415 662,898 1,104,830 1,325,796 1,657,245 2,209,660 3,314,490 and 6,628,980, with no remainder.
Since 6,628,980 cannot be divided by just 1 and 6,628,980, it is not a prime number.