(1) Real property sold subject to redemption, as provided in RCW 6.21.080, or any part thereof separately sold, may be redeemed by the following persons, or their successors in interest:

(a) The judgment debtor, in the whole or any part of the property separately sold.

(b) A creditor having a lien by judgment, decree, deed of trust, or mortgage, on any portion of the property, or any portion of any part thereof, separately sold, subsequent in priority to that on which the property was sold. The persons mentioned in this subsection are termed redemptioners.

(2) As used in this chapter, the terms "judgment debtor," "redemptioner," and "purchaser" refer also to their respective successors in interest.