Three of the following four numbers are alike in a certain way and one is different. Select the number that is different from the rest.

2105 6457 4328 3124

6457

2105 ⇒ 2 - 10 - 5 = 2 × 5 → 10 = middle number 6457 ⇒ 6 - 45 - 7 = 6 × 7 → 42 ≠ middle number 4328 ⇒ 4 - 32 - 8 = 4 × 8 → 32 = middle number 3124 ⇒ 3 - 12 - 4 = 3 × 4 → 12 = middle number