Nineteen is the seventh Mersenne prime exponent.
It is also a Keith number, recurring in a Fibonacci-like sequence started from its base 10 digits: 1, 9, 10, 19...
Nineteen is a centered triangular number, centered hexagonal number, and an octahedral number.
Every positive integer is the sum of at most nineteen fourth powers.
Nineteen is a Heegner number.
Nineteen is the atomic number of potassium.
The nineteenth state to enter the Union was Indiana.
The Soviet submarine K-19 was the first Soviet nuclear ballistic submarine.
I-19 is the designation for a U.S. interstate highway in Arizona.
19 years is very close to 235 lunations.
There are nineteen years between 15 August 1985 and 15 August 2004 (or, alternatively, 6,940 days, 166,560 hours, 9,993,600 minutes, or 599,616,000 seconds).
I am now nineteen years