215613661 has 4 divisors (see below), whose sum is σ = 224988192. Its totient is φ = 206239132.

The previous prime is 215613647. The next prime is 215613679. The reversal of 215613661 is 166316512.

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 215613661 - 2⁹ = 215613149 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (215613631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4687231 + ... + 4687276.

It is an arithmetic number, because the mean of its divisors is an integer number (56247048).

Almost surely, 2^215613661 is an apocalyptic number.

It is an amenable number.

215613661 is a deficient number, since it is larger than the sum of its proper divisors (9374531).

215613661 is an equidigital number, since it uses as much as digits as its factorization.

215613661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9374530.

The product of its digits is 6480, while the sum is 31.

The square root of 215613661 is about 14683.7890546003. The cubic root of 215613661 is about 599.6420652173.

The spelling of 215613661 in words is "two hundred fifteen million, six hundred thirteen thousand, six hundred sixty-one".