21804005 has 32 divisors (see below), whose sum is σ = 28643328. Its totient is φ = 15897600.

The previous prime is 21803983. The next prime is 21804007. The reversal of 21804005 is 50040812.

It is not a de Polignac number, because 21804005 - 2⁶ = 21803941 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21804007) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 298649 + ... + 298721.

It is an arithmetic number, because the mean of its divisors is an integer number (895104).

Almost surely, 2^21804005 is an apocalyptic number.

It is an amenable number.

21804005 is a deficient number, since it is larger than the sum of its proper divisors (6839323).

21804005 is a wasteful number, since it uses less digits than its factorization.

21804005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 197.

The product of its (nonzero) digits is 320, while the sum is 20.

The square root of 21804005 is about 4669.4758806530. The cubic root of 21804005 is about 279.3693501986.

Adding to 21804005 its reverse (50040812), we get a palindrome (71844817).

The spelling of 21804005 in words is "twenty-one million, eight hundred four thousand, five".