21216804 has 36 divisors (see below), whose sum is σ = 57590064. Its totient is φ = 6061776.

The previous prime is 21216791. The next prime is 21216809. The reversal of 21216804 is 40861212.

It is not an unprimeable number, because it can be changed into a prime (21216809) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 17454 + ... + 18629.

It is an arithmetic number, because the mean of its divisors is an integer number (1599724).

Almost surely, 2^21216804 is an apocalyptic number.

It is an amenable number.

21216804 is an abundant number, since it is smaller than the sum of its proper divisors (36373260).

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

21216804 is a wasteful number, since it uses less digits than its factorization.

21216804 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36104 (or 36095 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 24.

The square root of 21216804 is about 4606.1702096210. The cubic root of 21216804 is about 276.8386066914.

The spelling of 21216804 in words is "twenty-one million, two hundred sixteen thousand, eight hundred four".