A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 675675 can be evenly divided by 1 3 5 7 9 11 13 15 21 25 27 33 35 39 45 55 63 65 75 77 91 99 105 117 135 143 165 175 189 195 225 231 273 275 297 315 325 351 385 429 455 495 525 585 675 693 715 819 825 945 975 1,001 1,155 1,287 1,365 1,485 1,575 1,755 1,925 2,079 2,145 2,275 2,457 2,475 2,925 3,003 3,465 3,575 3,861 4,095 4,725 5,005 5,775 6,435 6,825 7,425 8,775 9,009 10,395 10,725 12,285 15,015 17,325 19,305 20,475 25,025 27,027 32,175 45,045 51,975 61,425 75,075 96,525 135,135 225,225 and 675,675, with no remainder.
Since 675,675 cannot be divided by just 1 and 675,675, it is not a prime number.