A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2767128 can be evenly divided by 1 2 3 4 6 7 8 12 13 14 21 24 26 28 39 42 49 52 56 78 84 91 98 104 147 156 168 181 182 196 273 294 312 362 364 392 543 546 588 637 724 728 1,086 1,092 1,176 1,267 1,274 1,448 1,911 2,172 2,184 2,353 2,534 2,548 3,801 3,822 4,344 4,706 5,068 5,096 7,059 7,602 7,644 8,869 9,412 10,136 14,118 15,204 15,288 16,471 17,738 18,824 26,607 28,236 30,408 32,942 35,476 49,413 53,214 56,472 65,884 70,952 98,826 106,428 115,297 131,768 197,652 212,856 230,594 345,891 395,304 461,188 691,782 922,376 1,383,564 and 2,767,128, with no remainder.
Since 2,767,128 cannot be divided by just 1 and 2,767,128, it is not a prime number.