A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3305760 can be evenly divided by 1 2 3 4 5 6 8 10 12 15 16 20 24 30 32 40 48 60 71 80 96 97 120 142 160 194 213 240 284 291 355 388 426 480 485 568 582 710 776 852 970 1,065 1,136 1,164 1,420 1,455 1,552 1,704 1,940 2,130 2,272 2,328 2,840 2,910 3,104 3,408 3,880 4,260 4,656 5,680 5,820 6,816 6,887 7,760 8,520 9,312 11,360 11,640 13,774 15,520 17,040 20,661 23,280 27,548 34,080 34,435 41,322 46,560 55,096 68,870 82,644 103,305 110,192 137,740 165,288 206,610 220,384 275,480 330,576 413,220 550,960 661,152 826,440 1,101,920 1,652,880 and 3,305,760, with no remainder.
Since 3,305,760 cannot be divided by just 1 and 3,305,760, it is not a prime number.