21811233 has 4 divisors (see below), whose sum is σ = 29081648. Its totient is φ = 14540820.

The previous prime is 21811211. The next prime is 21811261. The reversal of 21811233 is 33211812.

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 21811233 - 2¹⁶ = 21745697 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21811033) 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, 3635203 + ... + 3635208.

It is an arithmetic number, because the mean of its divisors is an integer number (7270412).

Almost surely, 2^21811233 is an apocalyptic number.

It is an amenable number.

21811233 is a deficient number, since it is larger than the sum of its proper divisors (7270415).

21811233 is an equidigital number, since it uses as much as digits as its factorization.

21811233 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7270414.

The product of its digits is 288, while the sum is 21.

The square root of 21811233 is about 4670.2497791874. The cubic root of 21811233 is about 279.4002169832.

The spelling of 21811233 in words is "twenty-one million, eight hundred eleven thousand, two hundred thirty-three".