Thanks in advance

I have a row that that is sometimes blank or contains a number followed by a
space and two letters eg. In cell A1 I have the value 456 CR

In cell B1 I am using the formula =IF( ISBLANK(A1),0,(LEFT(A1,
LEN(A1)-3)*1)) to strip the space and two letters from the cell. I multiply
(LEFT(A1, LEN(A1)-3) by 1 to convert to a number from text.

I am almost happy with the formula. I want the first part of the IF
statement to evaluate to 0 if the field is blank but do not want to see the
0. If I use "" instead of 0 it is a text value again which causes number
calculations to fail that use this cell.

How can I put a blank number value in the IF statement above?