A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2618352 can be evenly divided by 1 2 3 4 6 8 9 11 12 16 18 19 22 24 27 29 33 36 38 44 48 54 57 58 66 72 76 87 88 99 108 114 116 132 144 152 171 174 176 198 209 216 228 232 261 264 297 304 319 342 348 396 418 432 456 464 513 522 528 551 594 627 638 684 696 783 792 836 912 957 1,026 1,044 1,102 1,188 1,254 1,276 1,368 1,392 1,566 1,584 1,653 1,672 1,881 1,914 2,052 2,088 2,204 2,376 2,508 2,552 2,736 2,871 3,132 3,306 3,344 3,762 3,828 4,104 4,176 4,408 4,752 4,959 5,016 5,104 5,643 5,742 6,061 6,264 6,612 7,524 7,656 8,208 8,613 8,816 9,918 10,032 11,286 11,484 12,122 12,528 13,224 14,877 15,048 15,312 17,226 18,183 19,836 22,572 22,968 24,244 26,448 29,754 30,096 34,452 36,366 39,672 45,144 45,936 48,488 54,549 59,508 68,904 72,732 79,344 90,288 96,976 109,098 119,016 137,808 145,464 163,647 218,196 238,032 290,928 327,294 436,392 654,588 872,784 1,309,176 and 2,618,352, with no remainder.
Since 2,618,352 cannot be divided by just 1 and 2,618,352, it is not a prime number.