A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 5280264 can be evenly divided by 1 2 3 4 6 8 9 11 12 18 22 24 33 36 44 59 66 72 88 99 113 118 132 177 198 226 236 264 339 354 396 452 472 531 649 678 708 792 904 1,017 1,062 1,243 1,298 1,356 1,416 1,947 2,034 2,124 2,486 2,596 2,712 3,729 3,894 4,068 4,248 4,972 5,192 5,841 6,667 7,458 7,788 8,136 9,944 11,187 11,682 13,334 14,916 15,576 20,001 22,374 23,364 26,668 29,832 40,002 44,748 46,728 53,336 60,003 73,337 80,004 89,496 120,006 146,674 160,008 220,011 240,012 293,348 440,022 480,024 586,696 660,033 880,044 1,320,066 1,760,088 2,640,132 and 5,280,264, with no remainder.
Since 5,280,264 cannot be divided by just 1 and 5,280,264, it is not a prime number.