# Tag Archives: 2017

While idly thinking while heading back from the office, and then more later while thinking after dinner with my academic little brother Alex Walker and my future academic little sister-in-law Sara Schulz, we began to think about $2017$, the number.

## General Patterns

• 2017 is a prime number. 2017 is the 306th prime. The 2017th prime is 17539.
• As 2011 is also prime, we call 2017 a sexy prime.
• 2017 can be written as a sum of two squares,
$$2017 = 9^2 +44^2,$$
and this is the only way to write it as a sum of two squares.
• Similarly, 2017 appears as the hypotenuse of a primitive Pythagorean triangle,
$$2017^2 = 792^2 + 1855^2,$$
and this is the only such right triangle.
• 2017 is uniquely identified as the first odd prime that leaves a remainder of $2$ when divided by $5$, $13$, and $31$. That is,
$$2017 \equiv 2 \pmod {5, 13, 31}.$$
• In different bases,
\begin{align} (2017)_{10} &= (2681)_9 = (3741)_8 = (5611)_7 = (13201)_6 \notag \\ &= (31032)_5 = (133201)_4 = (2202201)_3 = (11111100001)_2 \notag \end{align}
The base $2$ and base $3$ expressions are sort of nice, including repetition.
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