Formula to only return a number value in a column with mixed Alpha and Numeric values

Hello everyone

Could I have some help to construct a formula that will return the number part of a mixed value cell; and only if that cell starts with a number. Otherwise return "".
I have tried this formula, but it only excludes the 0 value and not the cells beginning with alpha values.

=If(D5>0,D5,"")

Many, many thank yous to those with more expertise and patience than me.

Thank you ProtonLeah - I thought the formula was complete, but this is even better as it gives the number only - Fantastic - may you both have fabulous days for your help