⇒ 42 = 2 × 3 × 7

Hence if a number is divisible by 42 then it must be divisible by 2, 3 and 7.

For a number to be divisible by 2, last DIGIT of a number should be 2, 4, 6 or 8.

2646, 1008, 1470, 656, 2478 and 1826 all numbers are divisible by 2.

For a number to be divisible by 3 if the sum of the digits is divisible by 3.

⇒ 2646 = 2 + 6 + 4 + 6 = 18(Divisible by 3)

⇒ 1008 = 1 + 0 + 0 + 8 = 9(Divisible by 3)

⇒ 1470 = 1 + 4 + 7 + 0 = 12(Divisible by 3)

⇒ 656 = 6 + 5 + 6 = 17 (Not divisible by 3)

⇒ 2478 = 2 + 4 + 7 + 8 = 21(Divisible by 3)

⇒ 1826 = 1 + 8 + 2 + 6 = 17(Not divisible by 3)

Divisibility rule of 7(Subtract twice the last digit from the number formed by the remaining digit)

⇒ 2646 = 264 - (2 × 6) = 264 - 12 = 252(Divisible by 7)

⇒ 1008 = 100 - (2 × 8) = 100 - 16 = 84 (Divisible by 7)

⇒ 1470 = 147 - (0 × 2) = 147 (Divisible by 7)

⇒ 656 = 65 - (6 × 2) = 65 - 12 = 53 (Not divisible by 7)

⇒ 2478 = 247 - (2 × 8) = 247 - 16 = 231(Divisible by 7)

⇒ 1826 = 182 - 6 × 2 = 182 - 12 = 170(Not divisible by 7)

So, the numbers which are divisible by 42 are 2646, 1008, 1470 and 2478.