856815977 has 2 divisors, whose sum is σ = 856815978. Its totient is φ = 856815976.

The previous prime is 856815959. The next prime is 856815989. The reversal of 856815977 is 779518658.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 856381696 + 434281 = 29264^2 + 659^2 .

It is a cyclic number.

It is not a de Polignac number, because 856815977 - 2²⁴ = 840038761 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (856815907) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 428407988 + 428407989.

It is an arithmetic number, because the mean of its divisors is an integer number (428407989).

Almost surely, 2^856815977 is an apocalyptic number.

It is an amenable number.

856815977 is a deficient number, since it is larger than the sum of its proper divisors (1).

856815977 is an equidigital number, since it uses as much as digits as its factorization.

856815977 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4233600, while the sum is 56.

The square root of 856815977 is about 29271.4191148977. The cubic root of 856815977 is about 949.7934830872.

The spelling of 856815977 in words is "eight hundred fifty-six million, eight hundred fifteen thousand, nine hundred seventy-seven".