A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2759328 can be evenly divided by 1 2 3 4 6 8 9 11 12 13 16 18 22 24 26 32 33 36 39 44 48 52 66 67 72 78 88 96 99 104 117 132 134 143 144 156 176 198 201 208 234 264 268 286 288 312 352 396 402 416 429 468 528 536 572 603 624 737 792 804 858 871 936 1,056 1,072 1,144 1,206 1,248 1,287 1,474 1,584 1,608 1,716 1,742 1,872 2,144 2,211 2,288 2,412 2,574 2,613 2,948 3,168 3,216 3,432 3,484 3,744 4,422 4,576 4,824 5,148 5,226 5,896 6,432 6,633 6,864 6,968 7,839 8,844 9,581 9,648 10,296 10,452 11,792 13,266 13,728 13,936 15,678 17,688 19,162 19,296 20,592 20,904 23,584 26,532 27,872 28,743 31,356 35,376 38,324 41,184 41,808 53,064 57,486 62,712 70,752 76,648 83,616 86,229 106,128 114,972 125,424 153,296 172,458 212,256 229,944 250,848 306,592 344,916 459,888 689,832 919,776 1,379,664 and 2,759,328, with no remainder.
Since 2,759,328 cannot be divided by just 1 and 2,759,328, it is not a prime number.