A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2681760 can be evenly divided by 1 2 3 4 5 6 8 10 12 15 16 20 24 30 32 37 40 48 60 74 80 96 111 120 148 151 160 185 222 240 296 302 370 444 453 480 555 592 604 740 755 888 906 1,110 1,184 1,208 1,480 1,510 1,776 1,812 2,220 2,265 2,416 2,960 3,020 3,552 3,624 4,440 4,530 4,832 5,587 5,920 6,040 7,248 8,880 9,060 11,174 12,080 14,496 16,761 17,760 18,120 22,348 24,160 27,935 33,522 36,240 44,696 55,870 67,044 72,480 83,805 89,392 111,740 134,088 167,610 178,784 223,480 268,176 335,220 446,960 536,352 670,440 893,920 1,340,880 and 2,681,760, with no remainder.
Since 2,681,760 cannot be divided by just 1 and 2,681,760, it is not a prime number.