16565 has 4 divisors (see below), whose sum is σ = 19884. Its totient is φ = 13248.

The previous prime is 16561. The next prime is 16567. The reversal of 16565 is 56561.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 56561 = 163 ⋅347.

It can be written as a sum of positive squares in 2 ways, for example, as 11236 + 5329 = 106^2 + 73^2 .

It is a cyclic number.

It is not a de Polignac number, because 16565 - 2² = 16561 is a prime.

It is an Ulam number.

It is an alternating number because its digits alternate between odd and even.

It is a Duffinian number.

It is a plaindrome in base 11.

It is a self number, because there is not a number n which added to its sum of digits gives 16565.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16561) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1652 + ... + 1661.

It is an arithmetic number, because the mean of its divisors is an integer number (4971).

2¹⁶⁵⁶⁵ is an apocalyptic number.

It is an amenable number.

16565 is a deficient number, since it is larger than the sum of its proper divisors (3319).

16565 is an equidigital number, since it uses as much as digits as its factorization.

16565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3318.

The product of its digits is 900, while the sum is 23.

The square root of 16565 is about 128.7050892545. The cubic root of 16565 is about 25.4916030279.

It can be divided in two parts, 1656 and 5, that added together give a palindrome (1661).

The spelling of 16565 in words is "sixteen thousand, five hundred sixty-five".