21821804 has 24 divisors (see below), whose sum is σ = 41588400. Its totient is φ = 9979200.

The previous prime is 21821797. The next prime is 21821819. The reversal of 21821804 is 40812812.

It is a super-2 number, since 2×21821804² = 952382259628832, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2747 + ... + 7154.

It is an arithmetic number, because the mean of its divisors is an integer number (1732850).

Almost surely, 2^21821804 is an apocalyptic number.

It is an amenable number.

21821804 is a deficient number, since it is larger than the sum of its proper divisors (19766596).

21821804 is a wasteful number, since it uses less digits than its factorization.

21821804 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9953 (or 9951 counting only the distinct ones).

The product of its (nonzero) digits is 1024, while the sum is 26.

The square root of 21821804 is about 4671.3813802771. The cubic root of 21821804 is about 279.4453475919.

It can be divided in two parts, 218 and 21804, that added together give a palindrome (22022).

The spelling of 21821804 in words is "twenty-one million, eight hundred twenty-one thousand, eight hundred four".