A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 4556640 can be evenly divided by 1 2 3 4 5 6 8 10 11 12 15 16 20 22 24 30 32 33 40 44 48 55 60 66 80 88 96 110 120 132 160 165 176 220 240 264 330 352 440 480 528 660 863 880 1,056 1,320 1,726 1,760 2,589 2,640 3,452 4,315 5,178 5,280 6,904 8,630 9,493 10,356 12,945 13,808 17,260 18,986 20,712 25,890 27,616 28,479 34,520 37,972 41,424 47,465 51,780 56,958 69,040 75,944 82,848 94,930 103,560 113,916 138,080 142,395 151,888 189,860 207,120 227,832 284,790 303,776 379,720 414,240 455,664 569,580 759,440 911,328 1,139,160 1,518,880 2,278,320 and 4,556,640, with no remainder.
Since 4,556,640 cannot be divided by just 1 and 4,556,640, it is not a prime number.