Mary Mahler, MD
Mary Mahler, MD is a Medical Oncology Physician in Philadelphia, PA, registered under NPI 1326703927. NPPES records them as a sole proprietor, meaning the practice is not incorporated as a separate legal entity.
Getting there
The practice address on file is 51 N 39TH ST, Philadelphia, PA 19104. We have not yet mapped what surrounds this office — parking, transit, and nearby pharmacies are added as our data collection reaches each location.
Credentials and Medicare
| Licence | State | Specialty |
|---|---|---|
| MD475737 | PA | Medical Oncology Physician primary |
This provider holds licence MD475737 issued in PA. A licence number in NPPES reflects what was filed at registration — it does not confirm the licence is still active today.
This NPI does not appear in the PECOS Medicare enrolment file. Providers who do not bill Medicare — or who bill only through a group's enrolment — will not appear here. It is not a sign of any problem with the registration.
What Medical Oncology covers
An internist who specializes in the diagnosis and treatment of all types of cancer and other benign and malignant tumors. This specialist decides on and administers therapy for these malignancies as well as consults with surgeons and radiotherapists on other treatments for cancer. NUCC Health Care Provider Taxonomy, code 207RX0202X
The taxonomy records how the provider classifies their own practice. It does not confirm which conditions they currently treat, whether they are accepting new patients, or which insurance they take — call the office for that.
Full NPPES record
An NPI-1 identifies a single person. It stays with the clinician for life, even if they move practice or change state, which is why the address on file can lag behind where they actually work today.
| NPI | 1326703927 valid check digit |
|---|---|
| Entity type | Individual (NPI-1) |
| Enumeration date | Nov 8, 2021 |
| Last updated | Nov 8, 2021 |
| Status | Active |
| Sole proprietor | Yes |
| Credential | MD |
| Practice address |
51 N 39TH ST Philadelphia, PA 19104 (215) 662-9801 |
| Mailing address |
1639 ADDISON ST Philadelphia, PA 19146 |
Number check
How the check works, step by step
Every NPI carries a Luhn check digit — the same scheme used on credit cards. CMS prefixes the number with 80840 before computing it, which marks it as a US health identifier.
| Digit | 8 | 0 | 8 | 4 | 0 | 1 | 3 | 2 | 6 | 7 | 0 | 3 | 9 | 2 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Doubled? | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 |
| Value | 8 | 0 | 8 | 8 | 0 | 2 | 3 | 4 | 6 | 5 | 0 | 6 | 9 | 4 |
Sum = 63 · next multiple of 10 = 70 · check digit = 7 · actual last digit = 7
A valid check digit only means the number is well-formed. It does not mean the provider is licensed, active, or in good standing — those are separate questions answered by the sections above.