A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 799260 can be evenly divided by 1 2 3 4 5 6 7 10 11 12 14 15 20 21 22 28 30 33 35 42 44 55 60 66 70 77 84 105 110 132 140 154 165 173 210 220 231 308 330 346 385 420 462 519 660 692 770 865 924 1,038 1,155 1,211 1,540 1,730 1,903 2,076 2,310 2,422 2,595 3,460 3,633 3,806 4,620 4,844 5,190 5,709 6,055 7,266 7,612 9,515 10,380 11,418 12,110 13,321 14,532 18,165 19,030 22,836 24,220 26,642 28,545 36,330 38,060 39,963 53,284 57,090 66,605 72,660 79,926 114,180 133,210 159,852 199,815 266,420 399,630 and 799,260, with no remainder.
Since 799,260 cannot be divided by just 1 and 799,260, it is not a prime number.