A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6816740 can be evenly divided by 1 2 4 5 7 10 14 20 23 28 29 35 46 58 70 73 92 115 116 140 145 146 161 203 230 290 292 322 365 406 460 511 580 644 667 730 805 812 1,015 1,022 1,334 1,460 1,610 1,679 2,030 2,044 2,117 2,555 2,668 3,220 3,335 3,358 4,060 4,234 4,669 5,110 6,670 6,716 8,395 8,468 9,338 10,220 10,585 11,753 13,340 14,819 16,790 18,676 21,170 23,345 23,506 29,638 33,580 42,340 46,690 47,012 48,691 58,765 59,276 74,095 93,380 97,382 117,530 148,190 194,764 235,060 243,455 296,380 340,837 486,910 681,674 973,820 1,363,348 1,704,185 3,408,370 and 6,816,740, with no remainder.
Since 6,816,740 cannot be divided by just 1 and 6,816,740, it is not a prime number.