A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 5187336 can be evenly divided by 1 2 3 4 6 7 8 11 12 14 21 22 24 28 33 42 44 49 56 66 77 84 88 98 132 147 154 168 196 231 264 294 308 392 401 462 539 588 616 802 924 1,078 1,176 1,203 1,604 1,617 1,848 2,156 2,406 2,807 3,208 3,234 4,312 4,411 4,812 5,614 6,468 8,421 8,822 9,624 11,228 12,936 13,233 16,842 17,644 19,649 22,456 26,466 30,877 33,684 35,288 39,298 52,932 58,947 61,754 67,368 78,596 92,631 105,864 117,894 123,508 157,192 185,262 216,139 235,788 247,016 370,524 432,278 471,576 648,417 741,048 864,556 1,296,834 1,729,112 2,593,668 and 5,187,336, with no remainder.
Since 5,187,336 cannot be divided by just 1 and 5,187,336, it is not a prime number.