# 541

This number is a prime.

The numerical weight of the name Israel. Note that 541, the 100th prime number, is the 10th hexagonal star number (i.e., Star of David). [McGough]

541 = prime((5*4*1)*(5+4+1) - π(541)). Note that 541 is the second number with this property. [Firoozbakht]

reversal(541) = 5! + 4! + 1. The prime 541 is the only odd number greater than one with this property. [Firoozbakht]

The truncated dodecahedron has 541 chiral stellations, the only Archimedean solid to have a prime number of chiral stellations. [Post]

541 = prime((5+4+1)^2). It is the smallest number with this property. [Kumar]

The height of One World Trade Center, including its spire, reaches a total height of 541 meters. [Wesolowski]

The only non-titanic prime of form 7*77*777*...*777...777 + 2, i.e., 541 = 7*77 + 2. [Loungrides]

The larger prime in the only known case of consecutive primes, (523, 541), that have the same sum of digits. Note that their concatenations in order and reverse order, i.e., 523541 and 541523, are both primes. [Loungrides]

3^541-1 is the largest known number n such that n and n+/-1 all have primitive roots. Are there any larger such n? [Xayah]

The smallest prime that can be written as the sum of the first n primes all of which are themselves the sum of the first n primes (541 = 5 + 17 + 41 + 197 + 281). [Hollesen]

(There are 10 curios for this number that have not yet been approved by an editor.)