A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3106272 can be evenly divided by 1 2 3 4 6 8 12 13 16 19 24 26 32 38 39 48 52 57 76 78 96 104 114 131 152 156 208 228 247 262 304 312 393 416 456 494 524 608 624 741 786 912 988 1,048 1,248 1,482 1,572 1,703 1,824 1,976 2,096 2,489 2,964 3,144 3,406 3,952 4,192 4,978 5,109 5,928 6,288 6,812 7,467 7,904 9,956 10,218 11,856 12,576 13,624 14,934 19,912 20,436 23,712 27,248 29,868 32,357 39,824 40,872 54,496 59,736 64,714 79,648 81,744 97,071 119,472 129,428 163,488 194,142 238,944 258,856 388,284 517,712 776,568 1,035,424 1,553,136 and 3,106,272, with no remainder.
Since 3,106,272 cannot be divided by just 1 and 3,106,272, it is not a prime number.