16561565 has 8 divisors (see below), whose sum is σ = 20097720. Its totient is φ = 13100032.

The previous prime is 16561549. The next prime is 16561577. The reversal of 16561565 is 56516561.

It can be written as a sum of positive squares in 4 ways, for example, as 264196 + 16297369 = 514^2 + 4037^2 .

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 16561565 - 2⁴ = 16561549 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18164 + ... + 19053.

It is an arithmetic number, because the mean of its divisors is an integer number (2512215).

Almost surely, 2^16561565 is an apocalyptic number.

It is an amenable number.

16561565 is a deficient number, since it is larger than the sum of its proper divisors (3536155).

16561565 is an equidigital number, since it uses as much as digits as its factorization.

16561565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37311.

The product of its digits is 27000, while the sum is 35.

The square root of 16561565 is about 4069.5902742168. The cubic root of 16561565 is about 254.8984088462.

The spelling of 16561565 in words is "sixteen million, five hundred sixty-one thousand, five hundred sixty-five".