A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2720718 can be evenly divided by 1 2 3 6 7 9 11 13 14 18 21 22 26 33 39 42 63 66 77 78 91 99 117 126 143 151 154 182 198 231 234 273 286 302 429 453 462 546 693 819 858 906 1,001 1,057 1,287 1,359 1,386 1,638 1,661 1,963 2,002 2,114 2,574 2,718 3,003 3,171 3,322 3,926 4,983 5,889 6,006 6,342 9,009 9,513 9,966 11,627 11,778 13,741 14,949 17,667 18,018 19,026 21,593 23,254 27,482 29,898 34,881 35,334 41,223 43,186 64,779 69,762 82,446 104,643 123,669 129,558 151,151 194,337 209,286 247,338 302,302 388,674 453,453 906,906 1,360,359 and 2,720,718, with no remainder.
Since 2,720,718 cannot be divided by just 1 and 2,720,718, it is not a prime number.