A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 852852 can be evenly divided by 1 2 3 4 6 7 11 12 13 14 21 22 26 28 33 39 42 44 52 66 71 77 78 84 91 132 142 143 154 156 182 213 231 273 284 286 308 364 426 429 462 497 546 572 781 852 858 923 924 994 1,001 1,092 1,491 1,562 1,716 1,846 1,988 2,002 2,343 2,769 2,982 3,003 3,124 3,692 4,004 4,686 5,467 5,538 5,964 6,006 6,461 9,372 10,153 10,934 11,076 12,012 12,922 16,401 19,383 20,306 21,868 25,844 30,459 32,802 38,766 40,612 60,918 65,604 71,071 77,532 121,836 142,142 213,213 284,284 426,426 and 852,852, with no remainder.
Since 852,852 cannot be divided by just 1 and 852,852, it is not a prime number.