Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum

Marc B Armstrong, M.D.

Internal Medicine Physician in Aberdeen, SD · enumerated 2014.

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

National Provider Identifier

1326453556

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Registry record

Entity type Individual (Type 1)

Name Marc B Armstrong

Credential M.D.

Sex Male

Practice address 305 S State St, Aberdeen, SD, 57401

Phone (605) 622-5100

Fax (605) 622-4030

Enumeration date Jun 26, 2014

Last updated in NPPES Mar 17, 2018

Taxonomy & licenses

390200000X Student in an Organized Health Care Education/Training Program Student, Health Care · License TRN16984 (FL) Secondary

207R00000X Internal Medicine Physician Allopathic & Osteopathic Physicians · License 10781 (SD) 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

How do I verify Marc Armstrong's NPI record?

Cross-check NPI 1326453556 against the official CMS registry at npiregistry.cms.hhs.gov. This page mirrors the same public NPPES data with a monthly snapshot.

Is NPI 1326453556 active?

Yes, as of the latest NPPES snapshot, NPI 1326453556 is active (record last updated 2018-03-17).

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Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2018-03-17.