19918312321 has 4 divisors (see below), whose sum is σ = 19918756612. Its totient is φ = 19917868032.

The previous prime is 19918312283. The next prime is 19918312333. The reversal of 19918312321 is 12321381991.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12321381991 = 19 ⋅648493789.

It can be written as a sum of positive squares in 2 ways, for example, as 3188183296 + 16730129025 = 56464^2 + 129345^2 .

It is a cyclic number.

It is not a de Polignac number, because 19918312321 - 2²⁵ = 19884757889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19918313321) 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, 146256 + ... + 247441.

It is an arithmetic number, because the mean of its divisors is an integer number (4979689153).

Almost surely, 2^19918312321 is an apocalyptic number.

It is an amenable number.

19918312321 is a deficient number, since it is larger than the sum of its proper divisors (444291).

19918312321 is an equidigital number, since it uses as much as digits as its factorization.

19918312321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 444290.

The product of its digits is 23328, while the sum is 40.

The spelling of 19918312321 in words is "nineteen billion, nine hundred eighteen million, three hundred twelve thousand, three hundred twenty-one".