20404021 has 4 divisors (see below), whose sum is σ = 22258944. Its totient is φ = 18549100.

The previous prime is 20404009. The next prime is 20404039. The reversal of 20404021 is 12040402.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20404021 - 2⁵ = 20403989 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20403992 and 20404010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20404421) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 927445 + ... + 927466.

It is an arithmetic number, because the mean of its divisors is an integer number (5564736).

Almost surely, 2^20404021 is an apocalyptic number.

It is an amenable number.

20404021 is a deficient number, since it is larger than the sum of its proper divisors (1854923).

20404021 is a wasteful number, since it uses less digits than its factorization.

20404021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1854922.

The product of its (nonzero) digits is 64, while the sum is 13.

The square root of 20404021 is about 4517.0810265037. The cubic root of 20404021 is about 273.2573929757.

Adding to 20404021 its reverse (12040402), we get a palindrome (32444423).

The spelling of 20404021 in words is "twenty million, four hundred four thousand, twenty-one".