3,457
Use the smallest digits first, making sure you save an odd one for the end.
3457 is the smallest odd number formed.
03458
135,607
3475
101 is the smallest 3 digit odd whole number
103
The smallest odd 7-digit number is 1,000,001 .If you also want the ones digit to be the sum of the thousands and ten-thousands digits,then the smallest odd 7-digit number that satisfies that additional requirement is 1,001,001,but it's no longer the smallest odd 7-digit number.
1000001 is the smallest 7 digit odd number...
As the number is odd it must end in an odd digit; the odd digits are 1, 3, 5, 7, 9 and the smallest is 1 which is the sum of 1 and 0. Thus the smallest 7-digit number which meets your criteria is 1,001,001
555
111111
336