A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3078504 can be evenly divided by 1 2 3 4 6 8 9 11 12 13 18 22 23 24 26 33 36 39 44 46 52 66 69 72 78 88 92 99 104 117 132 138 143 156 169 184 198 207 234 253 264 276 286 299 312 338 396 414 429 468 506 507 552 572 598 676 759 792 828 858 897 936 1,012 1,014 1,144 1,196 1,287 1,352 1,518 1,521 1,656 1,716 1,794 1,859 2,024 2,028 2,277 2,392 2,574 2,691 3,036 3,042 3,289 3,432 3,588 3,718 3,887 4,056 4,554 5,148 5,382 5,577 6,072 6,084 6,578 7,176 7,436 7,774 9,108 9,867 10,296 10,764 11,154 11,661 12,168 13,156 14,872 15,548 16,731 18,216 19,734 21,528 22,308 23,322 26,312 29,601 31,096 33,462 34,983 39,468 42,757 44,616 46,644 59,202 66,924 69,966 78,936 85,514 93,288 118,404 128,271 133,848 139,932 171,028 236,808 256,542 279,864 342,056 384,813 513,084 769,626 1,026,168 1,539,252 and 3,078,504, with no remainder.
Since 3,078,504 cannot be divided by just 1 and 3,078,504, it is not a prime number.