00000000593987980000000059398798 is a 16 character string. The last character is a check character for that string, calculated according ISO 7064 MOD 11-2. The string could be an ISNI according to ISO 27729.
In print an ISNI can be written as four blocks of four characters, in such cases often preceded by the string 'ISNI': ISNI 0000 0000 5939 8798
ISNI based link
- Wikimedia ("ISNI"=0000 0000 5939 8798)
ISNI based matchVIAF