16651566561 has 24 divisors (see below), whose sum is σ = 26250325824. Its totient is φ = 9359189280.

The previous prime is 16651566527. The next prime is 16651566563. The reversal of 16651566561 is 16566515661.

16651566561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 16651566561 - 2¹⁵ = 16651533793 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 16651566561.

It is not an unprimeable number, because it can be changed into a prime (16651566563) 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 23 ways as a sum of consecutive naturals, for example, 919525 + ... + 937458.

It is an arithmetic number, because the mean of its divisors is an integer number (1093763576).

Almost surely, 2^16651566561 is an apocalyptic number.

It is an amenable number.

16651566561 is a deficient number, since it is larger than the sum of its proper divisors (9598759263).

16651566561 is a wasteful number, since it uses less digits than its factorization.

16651566561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1857061 (or 1857054 counting only the distinct ones).

The product of its digits is 972000, while the sum is 48.

The spelling of 16651566561 in words is "sixteen billion, six hundred fifty-one million, five hundred sixty-six thousand, five hundred sixty-one".