216891 has 16 divisors (see below), whose sum is σ = 333600. Its totient is φ = 139104.

The previous prime is 216877. The next prime is 216899. The reversal of 216891 is 198612.

It is not a de Polignac number, because 216891 - 2⁵ = 216859 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (216899) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 645 + ... + 921.

It is an arithmetic number, because the mean of its divisors is an integer number (20850).

2²¹⁶⁸⁹¹ is an apocalyptic number.

216891 is a deficient number, since it is larger than the sum of its proper divisors (116709).

216891 is a wasteful number, since it uses less digits than its factorization.

216891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 315 (or 309 counting only the distinct ones).

The product of its digits is 864, while the sum is 27.

The square root of 216891 is about 465.7155784382. The cubic root of 216891 is about 60.0823868217.

The spelling of 216891 in words is "two hundred sixteen thousand, eight hundred ninety-one".