A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2751336 can be evenly divided by 1 2 3 4 6 7 8 9 12 14 18 21 24 28 36 42 53 56 63 72 84 103 106 126 159 168 206 212 252 309 318 371 412 424 477 504 618 636 721 742 824 927 954 1,113 1,236 1,272 1,442 1,484 1,854 1,908 2,163 2,226 2,472 2,884 2,968 3,339 3,708 3,816 4,326 4,452 5,459 5,768 6,489 6,678 7,416 8,652 8,904 10,918 12,978 13,356 16,377 17,304 21,836 25,956 26,712 32,754 38,213 43,672 49,131 51,912 65,508 76,426 98,262 114,639 131,016 152,852 196,524 229,278 305,704 343,917 393,048 458,556 687,834 917,112 1,375,668 and 2,751,336, with no remainder.
Since 2,751,336 cannot be divided by just 1 and 2,751,336, it is not a prime number.