A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 958500 can be evenly divided by 1 2 3 4 5 6 9 10 12 15 18 20 25 27 30 36 45 50 54 60 71 75 90 100 108 125 135 142 150 180 213 225 250 270 284 300 355 375 426 450 500 540 639 675 710 750 852 900 1,065 1,125 1,278 1,350 1,420 1,500 1,775 1,917 2,130 2,250 2,556 2,700 3,195 3,375 3,550 3,834 4,260 4,500 5,325 6,390 6,750 7,100 7,668 8,875 9,585 10,650 12,780 13,500 15,975 17,750 19,170 21,300 26,625 31,950 35,500 38,340 47,925 53,250 63,900 79,875 95,850 106,500 159,750 191,700 239,625 319,500 479,250 and 958,500, with no remainder.
Since 958,500 cannot be divided by just 1 and 958,500, it is not a prime number.