A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6608520 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 15 18 20 24 27 29 30 36 40 45 54 58 60 72 87 90 108 116 120 135 145 174 180 211 216 232 261 270 290 348 360 422 435 522 540 580 633 696 783 844 870 1,044 1,055 1,080 1,160 1,266 1,305 1,566 1,688 1,740 1,899 2,088 2,110 2,532 2,610 3,132 3,165 3,480 3,798 3,915 4,220 5,064 5,220 5,697 6,119 6,264 6,330 7,596 7,830 8,440 9,495 10,440 11,394 12,238 12,660 15,192 15,660 18,357 18,990 22,788 24,476 25,320 28,485 30,595 31,320 36,714 37,980 45,576 48,952 55,071 56,970 61,190 73,428 75,960 91,785 110,142 113,940 122,380 146,856 165,213 183,570 220,284 227,880 244,760 275,355 330,426 367,140 440,568 550,710 660,852 734,280 826,065 1,101,420 1,321,704 1,652,130 2,202,840 3,304,260 and 6,608,520, with no remainder.
Since 6,608,520 cannot be divided by just 1 and 6,608,520, it is not a prime number.