21756804 has 48 divisors (see below), whose sum is σ = 56101248. Its totient is φ = 6527488.

The previous prime is 21756803. The next prime is 21756811. The reversal of 21756804 is 40865712.

It is not an unprimeable number, because it can be changed into a prime (21756803) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2374 + ... + 7010.

It is an arithmetic number, because the mean of its divisors is an integer number (1168776).

Almost surely, 2^21756804 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21756804, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28050624).

21756804 is an abundant number, since it is smaller than the sum of its proper divisors (34344444).

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

21756804 is a wasteful number, since it uses less digits than its factorization.

21756804 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4684 (or 4682 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 33.

The square root of 21756804 is about 4664.4189348728. The cubic root of 21756804 is about 279.1676129569.

The spelling of 21756804 in words is "twenty-one million, seven hundred fifty-six thousand, eight hundred four".