20404821 has 4 divisors (see below), whose sum is σ = 27206432. Its totient is φ = 13603212.

The previous prime is 20404817. The next prime is 20404837. The reversal of 20404821 is 12840402.

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 not a de Polignac number, because 20404821 - 2² = 20404817 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20404801) 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, 3400801 + ... + 3400806.

It is an arithmetic number, because the mean of its divisors is an integer number (6801608).

Almost surely, 2^20404821 is an apocalyptic number.

It is an amenable number.

20404821 is a deficient number, since it is larger than the sum of its proper divisors (6801611).

20404821 is an equidigital number, since it uses as much as digits as its factorization.

20404821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6801610.

The product of its (nonzero) digits is 512, while the sum is 21.

The square root of 20404821 is about 4517.1695783975. The cubic root of 20404821 is about 273.2609642172.

The spelling of 20404821 in words is "twenty million, four hundred four thousand, eight hundred twenty-one".