A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 825240 can be evenly divided by 1 2 3 4 5 6 8 10 12 13 15 20 23 24 26 30 39 40 46 52 60 65 69 78 92 104 115 120 130 138 156 184 195 230 260 276 299 312 345 390 460 520 529 552 598 690 780 897 920 1,058 1,196 1,380 1,495 1,560 1,587 1,794 2,116 2,392 2,645 2,760 2,990 3,174 3,588 4,232 4,485 5,290 5,980 6,348 6,877 7,176 7,935 8,970 10,580 11,960 12,696 13,754 15,870 17,940 20,631 21,160 27,508 31,740 34,385 35,880 41,262 55,016 63,480 68,770 82,524 103,155 137,540 165,048 206,310 275,080 412,620 and 825,240, with no remainder.
Since 825,240 cannot be divided by just 1 and 825,240, it is not a prime number.