856521521 has 2 divisors, whose sum is σ = 856521522. Its totient is φ = 856521520.

The previous prime is 856521461. The next prime is 856521563. The reversal of 856521521 is 125125658.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 843089296 + 13432225 = 29036^2 + 3665^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-856521521 is a prime.

It is not a weakly prime, because it can be changed into another prime (856511521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 428260760 + 428260761.

It is an arithmetic number, because the mean of its divisors is an integer number (428260761).

Almost surely, 2^856521521 is an apocalyptic number.

It is an amenable number.

856521521 is a deficient number, since it is larger than the sum of its proper divisors (1).

856521521 is an equidigital number, since it uses as much as digits as its factorization.

856521521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 24000, while the sum is 35.

The square root of 856521521 is about 29266.3889299654. The cubic root of 856521521 is about 949.6846676429.

The spelling of 856521521 in words is "eight hundred fifty-six million, five hundred twenty-one thousand, five hundred twenty-one".