Today is January 19, 2019, 1/19/19!

The number 1.1919 can be expressed as the fraction $354/297$ and the repeated fraction $1.\overline{1919}$ is $118/99$. Such a rational day!

The number 11919 is itself composite, expressible in terms of the primes 3, 29, and 137.

Let’s dive into 11919’s 19 side!

The featured image is a 19-sided star, a design by my daughter that was inspired by the ceiling of one of the Taj Mahal’s entrances

This tiling from the tomb of Shaikh Salim Chisti comes close also

Whether they are 19 sided or not, they are still amazing.

19 is the 8th prime number. It is also a Pierpont prime, a number that can be written as $2^u 3^v + 1$ where in this case $u = 1$ and $v = 2$.

19 has a special significance in the Bahá’í world where the are 19 days in each month and 19 months in the year, with about $\sqrt{19}$ (intercalary) days leftover.

The sum of the integers 1 to 19 is 190 and the sum of the primes up to 19 is 100!

Any day is a good day to meditate on the amazing patterns around us, especially a cold and rainy January Saturday!

### Posted by charlescearl

Data scientist at Automattic.com.

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