A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 5129280 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 13 15 16 18 20 24 26 30 32 36 39 40 45 48 52 60 64 65 72 78 80 90 96 104 117 120 130 137 144 156 160 180 192 195 208 234 240 260 274 288 312 320 360 390 411 416 468 480 520 548 576 585 624 685 720 780 822 832 936 960 1,040 1,096 1,170 1,233 1,248 1,370 1,440 1,560 1,644 1,781 1,872 2,055 2,080 2,192 2,340 2,466 2,496 2,740 2,880 3,120 3,288 3,562 3,744 4,110 4,160 4,384 4,680 4,932 5,343 5,480 6,165 6,240 6,576 7,124 7,488 8,220 8,768 8,905 9,360 9,864 10,686 10,960 12,330 12,480 13,152 14,248 16,029 16,440 17,810 18,720 19,728 21,372 21,920 24,660 26,304 26,715 28,496 32,058 32,880 35,620 37,440 39,456 42,744 43,840 49,320 53,430 56,992 64,116 65,760 71,240 78,912 80,145 85,488 98,640 106,860 113,984 128,232 131,520 142,480 160,290 170,976 197,280 213,720 256,464 284,960 320,580 341,952 394,560 427,440 512,928 569,920 641,160 854,880 1,025,856 1,282,320 1,709,760 2,564,640 and 5,129,280, with no remainder.
Since 5,129,280 cannot be divided by just 1 and 5,129,280, it is not a prime number.