A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2756320 can be evenly divided by 1 2 4 5 7 8 10 14 16 20 23 28 32 35 40 46 56 70 80 92 107 112 115 140 160 161 184 214 224 230 280 322 368 428 460 535 560 644 736 749 805 856 920 1,070 1,120 1,288 1,498 1,610 1,712 1,840 2,140 2,461 2,576 2,996 3,220 3,424 3,680 3,745 4,280 4,922 5,152 5,992 6,440 7,490 8,560 9,844 11,984 12,305 12,880 14,980 17,120 17,227 19,688 23,968 24,610 25,760 29,960 34,454 39,376 49,220 59,920 68,908 78,752 86,135 98,440 119,840 137,816 172,270 196,880 275,632 344,540 393,760 551,264 689,080 1,378,160 and 2,756,320, with no remainder.
Since 2,756,320 cannot be divided by just 1 and 2,756,320, it is not a prime number.