Seventeen (17) is a positive integer one more than 16 and one less than 18.

## PropertiesEdit

17 is the seventh prime number, after 13. It is in a twin prime pair with 19.

17 is also a Fermat prime, between 5 and 257. As such, a regular polygon with 17 sides is constructible with a compass and straightedge.

17 is a Mersenne exponent producing 131071.

17 is associated with bad luck in Italian superstition.

Ironically, the prize for 2 correct final digits in the German lottery *Spiel 77* is equal to 17 euros.

## In googology Edit

In Greek-based number-naming systems, 17 is associated with prefix "**heptadeka-**", and with prefix "**septendec-**" in Latin systems.

Sbiis Saibian calls the number **heptaxis**, and it's equal to 10+7 using the addition.

17 is the 6th output of the Xi function, \(\Xi(6) = 17\).