21331911 has 4 divisors (see below), whose sum is σ = 28442552. Its totient is φ = 14221272.

The previous prime is 21331903. The next prime is 21331963. The reversal of 21331911 is 11913312.

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

It is not a de Polignac number, because 21331911 - 2³ = 21331903 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21331901) 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, 3555316 + ... + 3555321.

It is an arithmetic number, because the mean of its divisors is an integer number (7110638).

Almost surely, 2^21331911 is an apocalyptic number.

21331911 is a deficient number, since it is larger than the sum of its proper divisors (7110641).

21331911 is an equidigital number, since it uses as much as digits as its factorization.

21331911 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7110640.

The product of its digits is 162, while the sum is 21.

The square root of 21331911 is about 4618.6481788506. The cubic root of 21331911 is about 277.3383459104.

The spelling of 21331911 in words is "twenty-one million, three hundred thirty-one thousand, nine hundred eleven".