19440509891 has 6 divisors (see below), whose sum is σ = 21368494476. Its totient is φ = 17673190700.

The previous prime is 19440509849. The next prime is 19440509911. The reversal of 19440509891 is 19890504491.

It is not a de Polignac number, because 19440509891 - 2¹⁸ = 19440247747 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19440509801) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 80332565 + ... + 80332806.

It is an arithmetic number, because the mean of its divisors is an integer number (3561415746).

Almost surely, 2^19440509891 is an apocalyptic number.

19440509891 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

19440509891 is a deficient number, since it is larger than the sum of its proper divisors (1927984585).

19440509891 is a wasteful number, since it uses less digits than its factorization.

19440509891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 160665393 (or 160665382 counting only the distinct ones).

The product of its (nonzero) digits is 466560, while the sum is 50.

The spelling of 19440509891 in words is "nineteen billion, four hundred forty million, five hundred nine thousand, eight hundred ninety-one".