2143

This number is a prime.

The process of "slipping" from the Age of Pisces to the Age of Aquarius requires 2143 years. [Skinner]

For a good approximation of π, take the square root of the square root of the fraction 2143/22. It is accurate to eight decimal places. (Note that the numerator of this fraction is a prime number.) [Dobb]

The smaller of only two derangements of {1, 2, 3, 4} that is prime. The other is 2341. [Loungrides]