Variable: NPI_LUHN_PREFIX

const NPI_LUHN_PREFIX: "80840" = "80840"

The 80840 prefix prepended to a 10-digit NPI before the Luhn check (the CMS NPI check-digit rule - 80840 is the ISO 7812 issuer identifier for the US health-application namespace). A real NPI satisfies luhn("80840" + npi) ≡ 0 (mod 10).