title: Problem 432
date: 2013/06/15 13:00:00
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# [Problem 432](https://projecteuler.net/problem=432)
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[Xem đề gốc (tiếng Anh)](https://projecteuler.net/problem=432)

## **Tổng totient**

Tính $\sum_{n=1}^{10^{15}} \varphi(n) \pmod{10^9}$.

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