21780804 has 24 divisors (see below), whose sum is σ = 50905120. Its totient is φ = 7248384.

The previous prime is 21780779. The next prime is 21780809. The reversal of 21780804 is 40808712.

It is not an unprimeable number, because it can be changed into a prime (21780809) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9252 + ... + 11364.

Almost surely, 2^21780804 is an apocalyptic number.

It is an amenable number.

21780804 is an abundant number, since it is smaller than the sum of its proper divisors (29124316).

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

21780804 is a wasteful number, since it uses less digits than its factorization.

21780804 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2979 (or 2977 counting only the distinct ones).

The product of its (nonzero) digits is 3584, while the sum is 30.

The square root of 21780804 is about 4666.9908934987. The cubic root of 21780804 is about 279.2702254640.

The spelling of 21780804 in words is "twenty-one million, seven hundred eighty thousand, eight hundred four".