A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3340584 can be evenly divided by 1 2 3 4 6 8 9 12 13 18 24 26 36 39 43 52 72 78 83 86 104 117 129 156 166 172 234 249 258 312 332 344 387 468 498 516 559 664 747 774 936 996 1,032 1,079 1,118 1,494 1,548 1,677 1,992 2,158 2,236 2,988 3,096 3,237 3,354 3,569 4,316 4,472 5,031 5,976 6,474 6,708 7,138 8,632 9,711 10,062 10,707 12,948 13,416 14,276 19,422 20,124 21,414 25,896 28,552 32,121 38,844 40,248 42,828 46,397 64,242 77,688 85,656 92,794 128,484 139,191 185,588 256,968 278,382 371,176 417,573 556,764 835,146 1,113,528 1,670,292 and 3,340,584, with no remainder.
Since 3,340,584 cannot be divided by just 1 and 3,340,584, it is not a prime number.