21040005 has 16 divisors (see below), whose sum is σ = 38473344. Its totient is φ = 9618240.

The previous prime is 21040001. The next prime is 21040007. The reversal of 21040005 is 50004012.

It is not a de Polignac number, because 21040005 - 2² = 21040001 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21040001) 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, 100086 + ... + 100295.

It is an arithmetic number, because the mean of its divisors is an integer number (2404584).

Almost surely, 2^21040005 is an apocalyptic number.

It is an amenable number.

21040005 is a deficient number, since it is larger than the sum of its proper divisors (17433339).

21040005 is a wasteful number, since it uses less digits than its factorization.

21040005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 200396.

The product of its (nonzero) digits is 40, while the sum is 12.

The square root of 21040005 is about 4586.9385214978. The cubic root of 21040005 is about 276.0674981942.

Adding to 21040005 its reverse (50004012), we get a palindrome (71044017).

The spelling of 21040005 in words is "twenty-one million, forty thousand, five".