A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 5238540 can be evenly divided by 1 2 3 4 5 6 9 10 12 15 18 20 27 30 36 45 54 60 89 90 108 109 135 178 180 218 267 270 327 356 436 445 534 540 545 654 801 890 981 1,068 1,090 1,308 1,335 1,602 1,635 1,780 1,962 2,180 2,403 2,670 2,943 3,204 3,270 3,924 4,005 4,806 4,905 5,340 5,886 6,540 8,010 9,612 9,701 9,810 11,772 12,015 14,715 16,020 19,402 19,620 24,030 29,103 29,430 38,804 48,060 48,505 58,206 58,860 87,309 97,010 116,412 145,515 174,618 194,020 261,927 291,030 349,236 436,545 523,854 582,060 873,090 1,047,708 1,309,635 1,746,180 2,619,270 and 5,238,540, with no remainder.
Since 5,238,540 cannot be divided by just 1 and 5,238,540, it is not a prime number.