Deleting lines not starting with numbers with sed

Title says all

Thanks for your help

sed 'g/^[!0-9]/d' file

or

grep -v "^[!0-9]" file

I guess it should be:

sed '/^[^0-9]/d' file

OR

grep -v "^[^0-9]" file

grep "^[0-9]" file

this not remove empty lines

sed '/^[^0-9]/d' file

more good way

sed -n '/^[0-9]/p' file