A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1560960 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 15 16 18 20 24 30 32 36 40 45 48 60 64 72 80 90 96 120 128 144 160 180 192 240 271 288 320 360 384 480 542 576 640 720 813 960 1,084 1,152 1,355 1,440 1,626 1,920 2,168 2,439 2,710 2,880 3,252 4,065 4,336 4,878 5,420 5,760 6,504 8,130 8,672 9,756 10,840 12,195 13,008 16,260 17,344 19,512 21,680 24,390 26,016 32,520 34,688 39,024 43,360 48,780 52,032 65,040 78,048 86,720 97,560 104,064 130,080 156,096 173,440 195,120 260,160 312,192 390,240 520,320 780,480 and 1,560,960, with no remainder.
Since 1,560,960 cannot be divided by just 1 and 1,560,960, it is not a prime number.