21112891 has 4 divisors (see below), whose sum is σ = 21793984. Its totient is φ = 20431800.

The previous prime is 21112879. The next prime is 21112907. The reversal of 21112891 is 19821112.

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

It is a cyclic number.

It is not a de Polignac number, because 21112891 - 2⁵ = 21112859 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21112831) 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, 340500 + ... + 340561.

It is an arithmetic number, because the mean of its divisors is an integer number (5448496).

Almost surely, 2^21112891 is an apocalyptic number.

21112891 is a deficient number, since it is larger than the sum of its proper divisors (681093).

21112891 is an equidigital number, since it uses as much as digits as its factorization.

21112891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 681092.

The product of its digits is 288, while the sum is 25.

The square root of 21112891 is about 4594.8766033486. The cubic root of 21112891 is about 276.3859117057.

The spelling of 21112891 in words is "twenty-one million, one hundred twelve thousand, eight hundred ninety-one".