A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2159520 can be evenly divided by 1 2 3 4 5 6 8 10 11 12 15 16 20 22 24 30 32 33 40 44 48 55 60 66 80 88 96 110 120 132 160 165 176 220 240 264 330 352 409 440 480 528 660 818 880 1,056 1,227 1,320 1,636 1,760 2,045 2,454 2,640 3,272 4,090 4,499 4,908 5,280 6,135 6,544 8,180 8,998 9,816 12,270 13,088 13,497 16,360 17,996 19,632 22,495 24,540 26,994 32,720 35,992 39,264 44,990 49,080 53,988 65,440 67,485 71,984 89,980 98,160 107,976 134,970 143,968 179,960 196,320 215,952 269,940 359,920 431,904 539,880 719,840 1,079,760 and 2,159,520, with no remainder.
Since 2,159,520 cannot be divided by just 1 and 2,159,520, it is not a prime number.