Number of the day: 213881

Properties of the number 213881:

213881 is a cyclic number.
213881 is the 19116^th prime.
213881 has 15 antidivisors and 213880 totatives.
213881 has a prime digit sum 23 in base 10.
213881 = 106941² - 106940² is the difference of 2 nonnegative squares in 1 way.
213881 is the difference of 2 positive pentagonal numbers in 1 way.
213881 = 284² + 365² is the sum of 2 positive squares in 1 way.
213881 = 16² + 45² + 460² is the sum of 3 positive squares.
213881² = 52569² + 207320² is the sum of 2 positive squares in 1 way.
213881² is the sum of 3 positive squares.
213881 is a proper divisor of 1811²⁰ - 1.
213881 is an emirp in (at least) the following bases: 7, 14, 15, 16, 21, 30, 33, 35, 50, 58, 60, 61, 63, 66, 67, 69, 71, 74, 78, 82, 85, 89, 91, and 97.
213881 is palindromic in (at least) base 72.

The number 213881 belongs to the following On-Line Encyclopedia of Integer Sequences (OEIS) sequences (among others):

Sequence numbers and descriptions below are taken from OEIS.
A129908: Quotient of the decimal representation of concatenated twin primes divided by 3.
A129909: Primes that are the quotient of the decimal representation of concatenated twin primes divided by 3.
A244638: In the '3x+1' problem, primes which as starting values set new records for number of steps to reach 1, where a step means either 'divide by two' or 'triple plus one and then divide by two'.