You can enter it with an apostrophe in front to preserve the leading
zeros, i.e. '00333009. Or you could format the cell first to Text,
then enter 00333009. In both cases the number would be treated as a
text value, so you could not do any arithmetic directly on it.
Alternatively, you could enter 333009 and format the cell using Custom
as "00000000" and this will give you the leading zeros and this will
be treated as a number.
Hope this helps.
Pete