A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2765560 can be evenly divided by 1 2 4 5 7 8 10 14 17 20 28 34 35 40 49 56 68 70 83 85 98 119 136 140 166 170 196 238 245 280 332 340 392 415 476 490 581 595 664 680 830 833 952 980 1,162 1,190 1,411 1,660 1,666 1,960 2,324 2,380 2,822 2,905 3,320 3,332 4,067 4,165 4,648 4,760 5,644 5,810 6,664 7,055 8,134 8,330 9,877 11,288 11,620 14,110 16,268 16,660 19,754 20,335 23,240 28,220 32,536 33,320 39,508 40,670 49,385 56,440 69,139 79,016 81,340 98,770 138,278 162,680 197,540 276,556 345,695 395,080 553,112 691,390 1,382,780 and 2,765,560, with no remainder.
Since 2,765,560 cannot be divided by just 1 and 2,765,560, it is not a prime number.