A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 495936 can be evenly divided by 1 2 3 4 6 7 8 9 12 14 16 18 21 24 27 28 32 36 41 42 48 54 56 63 64 72 82 84 96 108 112 123 126 144 164 168 189 192 216 224 246 252 287 288 328 336 369 378 432 448 492 504 574 576 656 672 738 756 861 864 984 1,008 1,107 1,148 1,312 1,344 1,476 1,512 1,722 1,728 1,968 2,016 2,214 2,296 2,583 2,624 2,952 3,024 3,444 3,936 4,032 4,428 4,592 5,166 5,904 6,048 6,888 7,749 7,872 8,856 9,184 10,332 11,808 12,096 13,776 15,498 17,712 18,368 20,664 23,616 27,552 30,996 35,424 41,328 55,104 61,992 70,848 82,656 123,984 165,312 247,968 and 495,936, with no remainder.
Since 495,936 cannot be divided by just 1 and 495,936, it is not a prime number.