A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3561600 can be evenly divided by 1 2 3 4 5 6 7 8 10 12 14 15 16 20 21 24 25 28 30 32 35 40 42 48 50 53 56 60 64 70 75 80 84 96 100 105 106 112 120 128 140 150 159 160 168 175 192 200 210 212 224 240 265 280 300 318 320 336 350 371 384 400 420 424 448 480 525 530 560 600 636 640 672 700 742 795 800 840 848 896 960 1,050 1,060 1,113 1,120 1,200 1,272 1,325 1,344 1,400 1,484 1,590 1,600 1,680 1,696 1,855 1,920 2,100 2,120 2,226 2,240 2,400 2,544 2,650 2,688 2,800 2,968 3,180 3,200 3,360 3,392 3,710 3,975 4,200 4,240 4,452 4,480 4,800 5,088 5,300 5,565 5,600 5,936 6,360 6,720 6,784 7,420 7,950 8,400 8,480 8,904 9,275 9,600 10,176 10,600 11,130 11,200 11,872 12,720 13,440 14,840 15,900 16,800 16,960 17,808 18,550 20,352 21,200 22,260 22,400 23,744 25,440 27,825 29,680 31,800 33,600 33,920 35,616 37,100 42,400 44,520 47,488 50,880 55,650 59,360 63,600 67,200 71,232 74,200 84,800 89,040 101,760 111,300 118,720 127,200 142,464 148,400 169,600 178,080 222,600 237,440 254,400 296,800 356,160 445,200 508,800 593,600 712,320 890,400 1,187,200 1,780,800 and 3,561,600, with no remainder.
Since 3,561,600 cannot be divided by just 1 and 3,561,600, it is not a prime number.