A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2572320 can be evenly divided by 1 2 3 4 5 6 8 10 12 15 16 20 23 24 30 32 40 46 48 60 69 80 92 96 115 120 138 160 184 230 233 240 276 345 368 460 466 480 552 690 699 736 920 932 1,104 1,165 1,380 1,398 1,840 1,864 2,208 2,330 2,760 2,796 3,495 3,680 3,728 4,660 5,359 5,520 5,592 6,990 7,456 9,320 10,718 11,040 11,184 13,980 16,077 18,640 21,436 22,368 26,795 27,960 32,154 37,280 42,872 53,590 55,920 64,308 80,385 85,744 107,180 111,840 128,616 160,770 171,488 214,360 257,232 321,540 428,720 514,464 643,080 857,440 1,286,160 and 2,572,320, with no remainder.
Since 2,572,320 cannot be divided by just 1 and 2,572,320, it is not a prime number.