A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1509600 can be evenly divided by 1 2 3 4 5 6 8 10 12 15 16 17 20 24 25 30 32 34 37 40 48 50 51 60 68 74 75 80 85 96 100 102 111 120 136 148 150 160 170 185 200 204 222 240 255 272 296 300 340 370 400 408 425 444 480 510 544 555 592 600 629 680 740 800 816 850 888 925 1,020 1,110 1,184 1,200 1,258 1,275 1,360 1,480 1,632 1,700 1,776 1,850 1,887 2,040 2,220 2,400 2,516 2,550 2,720 2,775 2,960 3,145 3,400 3,552 3,700 3,774 4,080 4,440 5,032 5,100 5,550 5,920 6,290 6,800 7,400 7,548 8,160 8,880 9,435 10,064 10,200 11,100 12,580 13,600 14,800 15,096 15,725 17,760 18,870 20,128 20,400 22,200 25,160 29,600 30,192 31,450 37,740 40,800 44,400 47,175 50,320 60,384 62,900 75,480 88,800 94,350 100,640 125,800 150,960 188,700 251,600 301,920 377,400 503,200 754,800 and 1,509,600, with no remainder.
Since 1,509,600 cannot be divided by just 1 and 1,509,600, it is not a prime number.