21003804 has 36 divisors (see below), whose sum is σ = 53385696. Its totient is φ = 6962688.

The previous prime is 21003803. The next prime is 21003811. The reversal of 21003804 is 40830012.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21003803) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5437 + ... + 8459.

It is an arithmetic number, because the mean of its divisors is an integer number (1482936).

Almost surely, 2^21003804 is an apocalyptic number.

It is an amenable number.

21003804 is an abundant number, since it is smaller than the sum of its proper divisors (32381892).

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

21003804 is a wasteful number, since it uses less digits than its factorization.

21003804 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3226 (or 3221 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 18.

The square root of 21003804 is about 4582.9907265889. The cubic root of 21003804 is about 275.9090752793.

Adding to 21003804 its reverse (40830012), we get a palindrome (61833816).

The spelling of 21003804 in words is "twenty-one million, three thousand, eight hundred four".