A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 142560 can be evenly divided by 1 2 3 4 5 6 8 9 10 11 12 15 16 18 20 22 24 27 30 32 33 36 40 44 45 48 54 55 60 66 72 80 81 88 90 96 99 108 110 120 132 135 144 160 162 165 176 180 198 216 220 240 264 270 288 297 324 330 352 360 396 405 432 440 480 495 528 540 594 648 660 720 792 810 864 880 891 990 1,056 1,080 1,188 1,296 1,320 1,440 1,485 1,584 1,620 1,760 1,782 1,980 2,160 2,376 2,592 2,640 2,970 3,168 3,240 3,564 3,960 4,320 4,455 4,752 5,280 5,940 6,480 7,128 7,920 8,910 9,504 11,880 12,960 14,256 15,840 17,820 23,760 28,512 35,640 47,520 71,280 and 142,560, with no remainder.
Since 142,560 cannot be divided by just 1 and 142,560, it is not a prime number.