21311020009 has 4 divisors (see below), whose sum is σ = 21311558100. Its totient is φ = 21310481920.

The previous prime is 21311019997. The next prime is 21311020039. The reversal of 21311020009 is 90002011312.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 19945347984 + 1365672025 = 141228^2 + 36955^2 .

It is a cyclic number.

It is not a de Polignac number, because 21311020009 - 2⁷ = 21311019881 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21311020039) 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, 204472 + ... + 290569.

It is an arithmetic number, because the mean of its divisors is an integer number (5327889525).

Almost surely, 2^21311020009 is an apocalyptic number.

It is an amenable number.

21311020009 is a deficient number, since it is larger than the sum of its proper divisors (538091).

21311020009 is an equidigital number, since it uses as much as digits as its factorization.

21311020009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 538090.

The product of its (nonzero) digits is 108, while the sum is 19.

The spelling of 21311020009 in words is "twenty-one billion, three hundred eleven million, twenty thousand, nine".