The digits within a ZIP code are not arbitrary; they follow a specific geographic logic established by the USPS:
: Identify a central mail processing facility.
List of 5 Digit ZIP Codes United States: American Postal Code
While "155787" is not a recognized standard five-digit ZIP code in the United States, it likely refers to a typo for , which belongs to Tamarack, Minnesota . Standard U.S. ZIP codes are restricted to five digits, ranging from 00501 to 99950. The Geography of Tamarack, MN (ZIP 55787)
: Specify a small post office or local delivery area. ZIP Code™ Lookup | USPS ZIP Code™ Lookup | USPS.