16561216791 has 96 divisors (see below), whose sum is σ = 30663959040. Its totient is φ = 8384643072.

The previous prime is 16561216783. The next prime is 16561216799. The reversal of 16561216791 is 19761216561.

16561216791 is a `hidden beast` number, since 1 + 6 + 561 + 2 + 16 + 79 + 1 = 666.

16561216791 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (16561216783) and next prime (16561216799).

It is not a de Polignac number, because 16561216791 - 2³ = 16561216783 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16561216799) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 3314391 + ... + 3319383.

It is an arithmetic number, because the mean of its divisors is an integer number (319416240).

Almost surely, 2^16561216791 is an apocalyptic number.

16561216791 is a deficient number, since it is larger than the sum of its proper divisors (14102742249).

16561216791 is a wasteful number, since it uses less digits than its factorization.

16561216791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5205 (or 5202 counting only the distinct ones).

The product of its digits is 136080, while the sum is 45.

The spelling of 16561216791 in words is "sixteen billion, five hundred sixty-one million, two hundred sixteen thousand, seven hundred ninety-one".