A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3042468 can be evenly divided by 1 2 3 4 6 9 11 12 13 18 22 26 27 33 36 39 44 52 54 66 78 99 108 117 132 143 156 197 198 234 286 297 351 394 396 429 468 572 591 594 702 788 858 1,182 1,188 1,287 1,404 1,716 1,773 2,167 2,364 2,561 2,574 3,546 3,861 4,334 5,122 5,148 5,319 6,501 7,092 7,683 7,722 8,668 10,244 10,638 13,002 15,366 15,444 19,503 21,276 23,049 26,004 28,171 30,732 39,006 46,098 56,342 58,509 69,147 78,012 84,513 92,196 112,684 117,018 138,294 169,026 234,036 253,539 276,588 338,052 507,078 760,617 1,014,156 1,521,234 and 3,042,468, with no remainder.
Since 3,042,468 cannot be divided by just 1 and 3,042,468, it is not a prime number.