A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2387088 can be evenly divided by 1 2 3 4 6 8 9 11 12 16 18 22 24 33 36 44 48 66 72 88 99 121 132 137 144 176 198 242 264 274 363 396 411 484 528 548 726 792 822 968 1,089 1,096 1,233 1,452 1,507 1,584 1,644 1,936 2,178 2,192 2,466 2,904 3,014 3,288 4,356 4,521 4,932 5,808 6,028 6,576 8,712 9,042 9,864 12,056 13,563 16,577 17,424 18,084 19,728 24,112 27,126 33,154 36,168 49,731 54,252 66,308 72,336 99,462 108,504 132,616 149,193 198,924 217,008 265,232 298,386 397,848 596,772 795,696 1,193,544 and 2,387,088, with no remainder.
Since 2,387,088 cannot be divided by just 1 and 2,387,088, it is not a prime number.