I want the sum of 3 numbers if all of the 3 cells contain numbers if not the value of the cell should be blank

=SUMIF(L2:N2,,L2:N2)
Range L2:N2 = {274.165," ", 35.057}
Criteria ???????
Sum_Range L2:N2

What would be the criteria to use to return a value or 0 or blank if L2:N2 is blank