216881 has 4 divisors (see below), whose sum is σ = 247872. Its totient is φ = 185892.

The previous prime is 216877. The next prime is 216899. The reversal of 216881 is 188612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 216881 - 2² = 216877 is a prime.

It is a super-2 number, since 2×216881² = 94074736322, which contains 22 as substring.

It is an Ulam number.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 216881.

It is not an unprimeable number, because it can be changed into a prime (216841) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15485 + ... + 15498.

It is an arithmetic number, because the mean of its divisors is an integer number (61968).

2²¹⁶⁸⁸¹ is an apocalyptic number.

It is an amenable number.

216881 is a deficient number, since it is larger than the sum of its proper divisors (30991).

216881 is an equidigital number, since it uses as much as digits as its factorization.

216881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30990.

The product of its digits is 768, while the sum is 26.

The square root of 216881 is about 465.7048421479. The cubic root of 216881 is about 60.0814634192.

The spelling of 216881 in words is "two hundred sixteen thousand, eight hundred eighty-one".