A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1035504 can be evenly divided by 1 2 3 4 6 8 9 12 16 17 18 24 27 34 36 47 48 51 54 68 72 81 94 102 108 136 141 144 153 162 188 204 216 272 282 306 324 376 408 423 432 459 564 612 648 752 799 816 846 918 1,128 1,224 1,269 1,296 1,377 1,598 1,692 1,836 2,256 2,397 2,448 2,538 2,754 3,196 3,384 3,672 3,807 4,794 5,076 5,508 6,392 6,768 7,191 7,344 7,614 9,588 10,152 11,016 12,784 14,382 15,228 19,176 20,304 21,573 22,032 28,764 30,456 38,352 43,146 57,528 60,912 64,719 86,292 115,056 129,438 172,584 258,876 345,168 517,752 and 1,035,504, with no remainder.
Since 1,035,504 cannot be divided by just 1 and 1,035,504, it is not a prime number.