21855812 has 48 divisors (see below), whose sum is σ = 44997120. Its totient is φ = 9177600.

The previous prime is 21855803. The next prime is 21855817.

It is a happy number.

21855812 is nontrivially palindromic in base 10.

It is not an unprimeable number, because it can be changed into a prime (21855817) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 45389 + ... + 45867.

It is an arithmetic number, because the mean of its divisors is an integer number (937440).

Almost surely, 2^21855812 is an apocalyptic number.

21855812 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

21855812 is an abundant number, since it is smaller than the sum of its proper divisors (23141308).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21855812 is a wasteful number, since it uses less digits than its factorization.

21855812 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 572 (or 570 counting only the distinct ones).

The product of its digits is 6400, while the sum is 32.

The square root of 21855812 is about 4675.0199999572. The cubic root of 21855812 is about 279.5904386338.

It can be divided in two parts, 2185 and 5812, that added together give a palindrome (7997).

The spelling of 21855812 in words is "twenty-one million, eight hundred fifty-five thousand, eight hundred twelve".