19640635321 has 4 divisors (see below), whose sum is σ = 19640952100. Its totient is φ = 19640318544.

The previous prime is 19640635303. The next prime is 19640635349. The reversal of 19640635321 is 12353604691.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12353604691 = 47 ⋅262842653.

It can be written as a sum of positive squares in 2 ways, for example, as 8974909696 + 10665725625 = 94736^2 + 103275^2 .

It is a cyclic number.

It is not a de Polignac number, because 19640635321 - 2³¹ = 17493151673 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19640635361) 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, 31506 + ... + 200683.

It is an arithmetic number, because the mean of its divisors is an integer number (4910238025).

Almost surely, 2^19640635321 is an apocalyptic number.

It is an amenable number.

19640635321 is a deficient number, since it is larger than the sum of its proper divisors (316779).

19640635321 is an equidigital number, since it uses as much as digits as its factorization.

19640635321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 316778.

The product of its (nonzero) digits is 116640, while the sum is 40.

The spelling of 19640635321 in words is "nineteen billion, six hundred forty million, six hundred thirty-five thousand, three hundred twenty-one".