A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 8242584 can be evenly divided by 1 2 3 4 6 7 8 12 14 21 24 28 42 43 49 56 84 86 98 129 147 163 168 172 196 258 294 301 326 344 392 489 516 588 602 652 903 978 1,032 1,141 1,176 1,204 1,304 1,806 1,956 2,107 2,282 2,408 3,423 3,612 3,912 4,214 4,564 6,321 6,846 7,009 7,224 7,987 8,428 9,128 12,642 13,692 14,018 15,974 16,856 21,027 23,961 25,284 27,384 28,036 31,948 42,054 47,922 49,063 50,568 56,072 63,896 84,108 95,844 98,126 147,189 168,216 191,688 196,252 294,378 343,441 392,504 588,756 686,882 1,030,323 1,177,512 1,373,764 2,060,646 2,747,528 4,121,292 and 8,242,584, with no remainder.
Since 8,242,584 cannot be divided by just 1 and 8,242,584, it is not a prime number.