A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6917120 can be evenly divided by 1 2 4 5 7 8 10 14 16 20 28 32 35 40 56 64 70 80 112 128 140 160 193 224 256 280 320 386 448 512 560 640 772 896 965 1,024 1,120 1,280 1,351 1,544 1,792 1,930 2,240 2,560 2,702 3,088 3,584 3,860 4,480 5,120 5,404 6,176 6,755 7,168 7,720 8,960 10,808 12,352 13,510 15,440 17,920 21,616 24,704 27,020 30,880 35,840 43,232 49,408 54,040 61,760 86,464 98,816 108,080 123,520 172,928 197,632 216,160 247,040 345,856 432,320 494,080 691,712 864,640 988,160 1,383,424 1,729,280 3,458,560 and 6,917,120, with no remainder.
Since 6,917,120 cannot be divided by just 1 and 6,917,120, it is not a prime number.