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Dr. Alexander John Greenstein, M.D.

Surgery Physician in New York, NY · enumerated 2008.

Data current as of Jul 13, 2026 · sourced from CMS NPPES

National Provider Identifier

1992964035

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Registry record

Entity type Individual (Type 1)
Name Dr. Alexander John Greenstein
Credential M.D.
Sex Male
Practice address 5 E 98th St, 15th Floor, Box 1259, New York, NY, 10029
Phone (212) 241-8679
Fax (212) 534-2654
Enumeration date Jun 4, 2008
Last updated in NPPES Oct 8, 2014

Taxonomy & licenses

208600000X Surgery Physician Allopathic & Osteopathic Physicians · License 60 233708 (NY) Primary
MD · Doctor of Medicine: A physician who completed medical school (allopathic medicine), residency training, and state licensure. About the MD credential

What is an NPI number?

A National Provider Identifier (NPI) is a unique 10-digit number that CMS assigns to every U.S. healthcare provider and organization under HIPAA. Type 1 NPIs identify individual providers; Type 2 NPIs identify organizations. The NPI appears on insurance claims, prescriptions, and credentialing paperwork, and never changes, even if the provider moves or changes specialty.

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Frequently asked questions

Is this the official NPI registry?
No. NPI Portal is a private site built on public CMS NPPES data. The official registry is npiregistry.cms.hhs.gov, operated by CMS.
What specialty is Alexander Greenstein?
Alexander Greenstein is registered in NPPES with the primary taxonomy of Surgery Physician. The taxonomy code describes the provider's classification and area of specialization for claims and credentialing.

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Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2014-10-08.