16561066561 has 8 divisors (see below), whose sum is σ = 18001678464. Its totient is φ = 15144266640.

The previous prime is 16561066547. The next prime is 16561066567. The reversal of 16561066561 is 16566016561.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 16561066561 - 2²¹ = 16558969409 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16561066567) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5951545 + ... + 5954326.

It is an arithmetic number, because the mean of its divisors is an integer number (2250209808).

Almost surely, 2^16561066561 is an apocalyptic number.

It is an amenable number.

16561066561 is a deficient number, since it is larger than the sum of its proper divisors (1440611903).

16561066561 is a wasteful number, since it uses less digits than its factorization.

16561066561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11905991.

The product of its (nonzero) digits is 194400, while the sum is 43.

The spelling of 16561066561 in words is "sixteen billion, five hundred sixty-one million, sixty-six thousand, five hundred sixty-one".