There are 6 places in 6 digit numbers.
Out of these 7 places two places are to be fixed for number 1.
This can be done in $^6C_2$ ways.
The remaining 4 places can be fixed by any of the two digits 2,3.
This can be done in $2^4$ ways
$\therefore$ The required number of 6 digit numbers= $2^4.^6C_2$