856618561 has 4 divisors (see below), whose sum is σ = 879770452. Its totient is φ = 833466672.

The previous prime is 856618541. The next prime is 856618571. The reversal of 856618561 is 165816658.

856618561 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.

It can be written as a sum of positive squares in 2 ways, for example, as 742235536 + 114383025 = 27244^2 + 10695^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-856618561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (856618531) 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, 11575890 + ... + 11575963.

It is an arithmetic number, because the mean of its divisors is an integer number (219942613).

Almost surely, 2^856618561 is an apocalyptic number.

It is an amenable number.

856618561 is a deficient number, since it is larger than the sum of its proper divisors (23151891).

856618561 is a wasteful number, since it uses less digits than its factorization.

856618561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23151890.

The product of its digits is 345600, while the sum is 46.

The square root of 856618561 is about 29268.0467575136. The cubic root of 856618561 is about 949.7205312757.

The spelling of 856618561 in words is "eight hundred fifty-six million, six hundred eighteen thousand, five hundred sixty-one".