A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3656835 can be evenly divided by 1 3 5 7 9 13 15 19 21 35 39 45 47 57 63 65 91 95 105 117 133 141 171 195 235 247 273 285 315 329 399 423 455 585 611 665 705 741 819 855 893 987 1,197 1,235 1,365 1,645 1,729 1,833 1,995 2,115 2,223 2,679 2,961 3,055 3,705 4,095 4,277 4,465 4,935 5,187 5,499 5,985 6,251 8,037 8,645 9,165 11,115 11,609 12,831 13,395 14,805 15,561 18,753 21,385 25,935 27,495 31,255 34,827 38,493 40,185 56,259 58,045 64,155 77,805 81,263 93,765 104,481 174,135 192,465 243,789 281,295 406,315 522,405 731,367 1,218,945 and 3,656,835, with no remainder.
Since 3,656,835 cannot be divided by just 1 and 3,656,835, it is not a prime number.