215845561 has 4 divisors (see below), whose sum is σ = 215889124. Its totient is φ = 215802000.

The previous prime is 215845493. The next prime is 215845571. The reversal of 215845561 is 165548512.

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 199685161 + 16160400 = 14131^2 + 4020^2 .

It is a cyclic number.

It is not a de Polignac number, because 215845561 - 2⁷ = 215845433 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 215845561.

It is not an unprimeable number, because it can be changed into a prime (215845571) 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, 13230 + ... + 24631.

It is an arithmetic number, because the mean of its divisors is an integer number (53972281).

Almost surely, 2^215845561 is an apocalyptic number.

It is an amenable number.

215845561 is a deficient number, since it is larger than the sum of its proper divisors (43563).

215845561 is an equidigital number, since it uses as much as digits as its factorization.

215845561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43562.

The product of its digits is 48000, while the sum is 37.

The square root of 215845561 is about 14691.6833957175. The cubic root of 215845561 is about 599.8569668312.

The spelling of 215845561 in words is "two hundred fifteen million, eight hundred forty-five thousand, five hundred sixty-one".