A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 8657370 can be evenly divided by 1 2 3 5 6 9 10 15 18 29 30 31 45 58 62 87 90 93 107 145 155 174 186 214 261 279 290 310 321 435 465 522 535 558 642 870 899 930 963 1,070 1,305 1,395 1,605 1,798 1,926 2,610 2,697 2,790 3,103 3,210 3,317 4,495 4,815 5,394 6,206 6,634 8,091 8,990 9,309 9,630 9,951 13,485 15,515 16,182 16,585 18,618 19,902 26,970 27,927 29,853 31,030 33,170 40,455 46,545 49,755 55,854 59,706 80,910 93,090 96,193 99,510 139,635 149,265 192,386 279,270 288,579 298,530 480,965 577,158 865,737 961,930 1,442,895 1,731,474 2,885,790 4,328,685 and 8,657,370, with no remainder.
Since 8,657,370 cannot be divided by just 1 and 8,657,370, it is not a prime number.