33. How many six-digit numbers are there in which all digits are odd?
33. The total number of different six-digit numbers is 900000. (How to determine this?) Of these, half end with an odd digit, i.e., 450000. Of these numbers, those with the second digit from the right being odd are $450000: 2=225000$, of which those with the third digit from the right being odd are $225000: 2=112500$, of which those with the fourth digit from the right being odd are 56250, of which those with the fifth digit from the right being odd are 28125, of which those with the sixth digit from the right being odd are $\frac{28125}{9} \cdot 5=15625$ (the sixth digit from the right, i.e., the first from the left, cannot be 0). Therefore, there are 15625 six-digit numbers where all digits are odd.