A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6938040 can be evenly divided by 1 2 3 4 5 6 8 10 12 15 17 19 20 24 30 34 38 40 51 57 60 68 76 85 95 102 114 120 136 152 170 179 190 204 228 255 285 323 340 358 380 408 456 510 537 570 646 680 716 760 895 969 1,020 1,074 1,140 1,292 1,432 1,615 1,790 1,938 2,040 2,148 2,280 2,584 2,685 3,043 3,230 3,401 3,580 3,876 4,296 4,845 5,370 6,086 6,460 6,802 7,160 7,752 9,129 9,690 10,203 10,740 12,172 12,920 13,604 15,215 17,005 18,258 19,380 20,406 21,480 24,344 27,208 30,430 34,010 36,516 38,760 40,812 45,645 51,015 57,817 60,860 68,020 73,032 81,624 91,290 102,030 115,634 121,720 136,040 173,451 182,580 204,060 231,268 289,085 346,902 365,160 408,120 462,536 578,170 693,804 867,255 1,156,340 1,387,608 1,734,510 2,312,680 3,469,020 and 6,938,040, with no remainder.
Since 6,938,040 cannot be divided by just 1 and 6,938,040, it is not a prime number.