216584561 has 4 divisors (see below), whose sum is σ = 217209072. Its totient is φ = 215960052.

The previous prime is 216584497. The next prime is 216584597. The reversal of 216584561 is 165485612.

It is a happy number.

216584561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 216584561 - 2⁶ = 216584497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (216587561) 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, 311735 + ... + 312428.

It is an arithmetic number, because the mean of its divisors is an integer number (54302268).

Almost surely, 2^216584561 is an apocalyptic number.

It is an amenable number.

216584561 is a deficient number, since it is larger than the sum of its proper divisors (624511).

216584561 is an equidigital number, since it uses as much as digits as its factorization.

216584561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 624510.

The product of its digits is 57600, while the sum is 38.

The square root of 216584561 is about 14716.8121887860. The cubic root of 216584561 is about 600.5407726470.

The spelling of 216584561 in words is "two hundred sixteen million, five hundred eighty-four thousand, five hundred sixty-one".