A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 7605720 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 15 18 20 24 30 36 37 40 45 60 72 74 90 111 120 148 180 185 222 296 333 360 370 444 555 571 666 740 888 1,110 1,142 1,332 1,480 1,665 1,713 2,220 2,284 2,664 2,855 3,330 3,426 4,440 4,568 5,139 5,710 6,660 6,852 8,565 10,278 11,420 13,320 13,704 17,130 20,556 21,127 22,840 25,695 34,260 41,112 42,254 51,390 63,381 68,520 84,508 102,780 105,635 126,762 169,016 190,143 205,560 211,270 253,524 316,905 380,286 422,540 507,048 633,810 760,572 845,080 950,715 1,267,620 1,521,144 1,901,430 2,535,240 3,802,860 and 7,605,720, with no remainder.
Since 7,605,720 cannot be divided by just 1 and 7,605,720, it is not a prime number.