Official solution
Except 1 and 2 there are eight options on first place and only one option at fourth place possible which is digit '2'.
Remaining three places can be filled by any three digits out of 1, 3, 4, 5, 6, 7, 8 and 9.
\[ \therefore \] No. of five digits numbers = 8 \[ \times \] 8 \[ \times \] 7 \[ \times \] 1 \[ \times \] 6 = 336 \[ \times \] 8
Also 336k = 336 \[ \times \] 8
\[ \Rightarrow \] k = 8