A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 8961540 can be evenly divided by 1 2 3 4 5 6 7 10 12 14 15 19 20 21 28 30 35 38 42 57 60 70 76 84 95 105 114 133 140 190 210 228 266 285 380 399 420 532 570 665 798 1,123 1,140 1,330 1,596 1,995 2,246 2,660 3,369 3,990 4,492 5,615 6,738 7,861 7,980 11,230 13,476 15,722 16,845 21,337 22,460 23,583 31,444 33,690 39,305 42,674 47,166 64,011 67,380 78,610 85,348 94,332 106,685 117,915 128,022 149,359 157,220 213,370 235,830 256,044 298,718 320,055 426,740 448,077 471,660 597,436 640,110 746,795 896,154 1,280,220 1,493,590 1,792,308 2,240,385 2,987,180 4,480,770 and 8,961,540, with no remainder.
Since 8,961,540 cannot be divided by just 1 and 8,961,540, it is not a prime number.