A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 860244 can be evenly divided by 1 2 3 4 6 7 11 12 14 19 21 22 28 33 38 42 44 49 57 66 76 77 84 98 114 132 133 147 154 196 209 228 231 266 294 308 343 399 418 462 532 539 588 627 686 798 836 924 931 1,029 1,078 1,254 1,372 1,463 1,596 1,617 1,862 2,058 2,156 2,508 2,793 2,926 3,234 3,724 3,773 4,116 4,389 5,586 5,852 6,468 6,517 7,546 8,778 10,241 11,172 11,319 13,034 15,092 17,556 19,551 20,482 22,638 26,068 30,723 39,102 40,964 45,276 61,446 71,687 78,204 122,892 143,374 215,061 286,748 430,122 and 860,244, with no remainder.
Since 860,244 cannot be divided by just 1 and 860,244, it is not a prime number.