7219

This number is a prime.

Just showing those entries submitted by 'Leonardis': (Click here to show all)

7219 = 19³ + 19² - 1, i.e. the only case when the cubic polynomial x³+x²-1 applied to the prime formed from its last two digits (19) gives back the original number. Note that it is also a permutation of the Hardy-Ramanujan number. [Leonardis]