A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3520920 can be evenly divided by 1 2 3 4 5 6 8 10 12 13 15 20 24 26 30 37 39 40 52 60 61 65 74 78 104 111 120 122 130 148 156 183 185 195 222 244 260 296 305 312 366 370 390 444 481 488 520 555 610 732 740 780 793 888 915 962 1,110 1,220 1,443 1,464 1,480 1,560 1,586 1,830 1,924 2,220 2,257 2,379 2,405 2,440 2,886 3,172 3,660 3,848 3,965 4,440 4,514 4,758 4,810 5,772 6,344 6,771 7,215 7,320 7,930 9,028 9,516 9,620 11,285 11,544 11,895 13,542 14,430 15,860 18,056 19,032 19,240 22,570 23,790 27,084 28,860 29,341 31,720 33,855 45,140 47,580 54,168 57,720 58,682 67,710 88,023 90,280 95,160 117,364 135,420 146,705 176,046 234,728 270,840 293,410 352,092 440,115 586,820 704,184 880,230 1,173,640 1,760,460 and 3,520,920, with no remainder.
Since 3,520,920 cannot be divided by just 1 and 3,520,920, it is not a prime number.