16518681561 has 32 divisors (see below), whose sum is σ = 23841941760. Its totient is φ = 10150043904.

The previous prime is 16518681551. The next prime is 16518681563.

16518681561 is nontrivially palindromic in base 10.

It is not a de Polignac number, because 16518681561 - 2¹⁸ = 16518419417 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 16518681561.

It is not an unprimeable number, because it can be changed into a prime (16518681563) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 122196 + ... + 219018.

It is an arithmetic number, because the mean of its divisors is an integer number (745060680).

Almost surely, 2^16518681561 is an apocalyptic number.

It is an amenable number.

16518681561 is a deficient number, since it is larger than the sum of its proper divisors (7323260199).

16518681561 is a wasteful number, since it uses less digits than its factorization.

16518681561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 96945.

The product of its digits is 345600, while the sum is 48.

The spelling of 16518681561 in words is "sixteen billion, five hundred eighteen million, six hundred eighty-one thousand, five hundred sixty-one".