Degradation of inorganic polyphosphates (polyP). Releases orthophosphate processively from the ends of the polyP chain. Prefers short-chain length polyphosphates as substrates. Can also hydrolyze ATP and ADP substrates, but lacks GTPase activity. Cannot hydrolyze pppGpp to ppGpp. [phosphate](n) + H2O = [phosphate](n-1) + H(+) + phosphate Can also use, to a lesser extent, Mg(2+) and Zn(2+). Exopolyphosphatase activity is inhibited by (p)ppGpp alarmones produced during the bacterial stringent response. kcat is 10.2 sec(-1) with polyP(14) as substrate. kcat is 7.3 sec(-1) with polyP(60) as substrate. kcat is 6.7 sec(-1) with polyP(130) as substrate. kcat is 1.9 sec(-1) with ATP as substrate. Homodimer. Belongs to the GppA/Ppx family. Truncated N-terminus.