20404811821 has 4 divisors (see below), whose sum is σ = 20486106144. Its totient is φ = 20323517500.

The previous prime is 20404811783. The next prime is 20404811863. The reversal of 20404811821 is 12811840402.

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 20404811821 - 2¹¹ = 20404809773 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 (20404811891) 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, 40646785 + ... + 40647286.

It is an arithmetic number, because the mean of its divisors is an integer number (5121526536).

Almost surely, 2^20404811821 is an apocalyptic number.

It is an amenable number.

20404811821 is a deficient number, since it is larger than the sum of its proper divisors (81294323).

20404811821 is an equidigital number, since it uses as much as digits as its factorization.

20404811821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81294322.

The product of its (nonzero) digits is 4096, while the sum is 31.

The spelling of 20404811821 in words is "twenty billion, four hundred four million, eight hundred eleven thousand, eight hundred twenty-one".