A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 955260 can be evenly divided by 1 2 3 4 5 6 9 10 12 15 18 20 27 29 30 36 45 54 58 60 61 87 90 108 116 122 135 145 174 180 183 244 261 270 290 305 348 366 435 522 540 549 580 610 732 783 870 915 1,044 1,098 1,220 1,305 1,566 1,647 1,740 1,769 1,830 2,196 2,610 2,745 3,132 3,294 3,538 3,660 3,915 5,220 5,307 5,490 6,588 7,076 7,830 8,235 8,845 10,614 10,980 15,660 15,921 16,470 17,690 21,228 26,535 31,842 32,940 35,380 47,763 53,070 63,684 79,605 95,526 106,140 159,210 191,052 238,815 318,420 477,630 and 955,260, with no remainder.
Since 955,260 cannot be divided by just 1 and 955,260, it is not a prime number.