856815961 has 4 divisors (see below), whose sum is σ = 856937124. Its totient is φ = 856694800.

The previous prime is 856815959. The next prime is 856815977. The reversal of 856815961 is 169518658.

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 242767561 + 614048400 = 15581^2 + 24780^2 .

It is a cyclic number.

It is not a de Polignac number, because 856815961 - 2¹ = 856815959 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (856815361) 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, 49270 + ... + 64351.

It is an arithmetic number, because the mean of its divisors is an integer number (214234281).

Almost surely, 2^856815961 is an apocalyptic number.

It is an amenable number.

856815961 is a deficient number, since it is larger than the sum of its proper divisors (121163).

856815961 is a wasteful number, since it uses less digits than its factorization.

856815961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 121162.

The product of its digits is 518400, while the sum is 49.

The square root of 856815961 is about 29271.4188415936. The cubic root of 856815961 is about 949.7934771751.

The spelling of 856815961 in words is "eight hundred fifty-six million, eight hundred fifteen thousand, nine hundred sixty-one".