A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1159488 can be evenly divided by 1 2 3 4 6 8 9 11 12 16 18 22 24 27 32 33 36 44 48 54 61 64 66 72 88 96 99 108 122 132 144 176 183 192 198 216 244 264 288 297 352 366 396 432 488 528 549 576 594 671 704 732 792 864 976 1,056 1,098 1,188 1,342 1,464 1,584 1,647 1,728 1,952 2,013 2,112 2,196 2,376 2,684 2,928 3,168 3,294 3,904 4,026 4,392 4,752 5,368 5,856 6,039 6,336 6,588 8,052 8,784 9,504 10,736 11,712 12,078 13,176 16,104 17,568 18,117 19,008 21,472 24,156 26,352 32,208 35,136 36,234 42,944 48,312 52,704 64,416 72,468 96,624 105,408 128,832 144,936 193,248 289,872 386,496 579,744 and 1,159,488, with no remainder.
Since 1,159,488 cannot be divided by just 1 and 1,159,488, it is not a prime number.