216565 has 4 divisors (see below), whose sum is σ = 259884. Its totient is φ = 173248.

The previous prime is 216553. The next prime is 216569. The reversal of 216565 is 565612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 167281 + 49284 = 409^2 + 222^2 .

It is a cyclic number.

It is not a de Polignac number, because 216565 - 2¹¹ = 214517 is a prime.

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

It is a Duffinian number.

It is a plaindrome in base 14.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216569) 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, 21652 + ... + 21661.

It is an arithmetic number, because the mean of its divisors is an integer number (64971).

2²¹⁶⁵⁶⁵ is an apocalyptic number.

It is an amenable number.

216565 is a deficient number, since it is larger than the sum of its proper divisors (43319).

216565 is an equidigital number, since it uses as much as digits as its factorization.

216565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43318.

The product of its digits is 1800, while the sum is 25.

The square root of 216565 is about 465.3654477935. The cubic root of 216565 is about 60.0522692670.

The spelling of 216565 in words is "two hundred sixteen thousand, five hundred sixty-five".