210891 has 4 divisors (see below), whose sum is σ = 281192. Its totient is φ = 140592.

The previous prime is 210869. The next prime is 210901. The reversal of 210891 is 198012.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 210891 - 2⁶ = 210827 is a prime.

It is a D-number.

It is a Duffinian number.

It is a plaindrome in base 11.

It is not an unprimeable number, because it can be changed into a prime (210811) 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, 35146 + ... + 35151.

It is an arithmetic number, because the mean of its divisors is an integer number (70298).

2²¹⁰⁸⁹¹ is an apocalyptic number.

210891 is a deficient number, since it is larger than the sum of its proper divisors (70301).

210891 is an equidigital number, since it uses as much as digits as its factorization.

210891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 70300.

The product of its (nonzero) digits is 144, while the sum is 21.

The square root of 210891 is about 459.2287011936. The cubic root of 210891 is about 59.5231649556.

The spelling of 210891 in words is "two hundred ten thousand, eight hundred ninety-one".