A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3358782 can be evenly divided by 1 2 3 6 7 9 14 18 19 21 23 38 42 46 57 61 63 69 114 122 126 133 138 161 171 183 207 266 322 342 366 399 414 427 437 483 549 798 854 874 966 1,098 1,159 1,197 1,281 1,311 1,403 1,449 2,318 2,394 2,562 2,622 2,806 2,898 3,059 3,477 3,843 3,933 4,209 6,118 6,954 7,686 7,866 8,113 8,418 9,177 9,821 10,431 12,627 16,226 18,354 19,642 20,862 24,339 25,254 26,657 27,531 29,463 48,678 53,314 55,062 58,926 73,017 79,971 88,389 146,034 159,942 176,778 186,599 239,913 373,198 479,826 559,797 1,119,594 1,679,391 and 3,358,782, with no remainder.
Since 3,358,782 cannot be divided by just 1 and 3,358,782, it is not a prime number.