A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3689640 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 90 111 120 148 180 185 222 277 296 333 360 370 444 554 555 666 740 831 888 1,108 1,110 1,332 1,385 1,480 1,662 1,665 2,216 2,220 2,493 2,664 2,770 3,324 3,330 4,155 4,440 4,986 5,540 6,648 6,660 8,310 9,972 10,249 11,080 12,465 13,320 16,620 19,944 20,498 24,930 30,747 33,240 40,996 49,860 51,245 61,494 81,992 92,241 99,720 102,490 122,988 153,735 184,482 204,980 245,976 307,470 368,964 409,960 461,205 614,940 737,928 922,410 1,229,880 1,844,820 and 3,689,640, with no remainder.
Since 3,689,640 cannot be divided by just 1 and 3,689,640, it is not a prime number.