815681681 has 2 divisors, whose sum is σ = 815681682. Its totient is φ = 815681680.

The previous prime is 815681639. The next prime is 815681693. The reversal of 815681681 is 186186518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 654899281 + 160782400 = 25591^2 + 12680^2 .

It is a cyclic number.

It is not a de Polignac number, because 815681681 - 2¹⁸ = 815419537 is a prime.

It is a super-2 number, since 2×815681681² = 1330673209437971522, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (815681621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 407840840 + 407840841.

It is an arithmetic number, because the mean of its divisors is an integer number (407840841).

Almost surely, 2^815681681 is an apocalyptic number.

It is an amenable number.

815681681 is a deficient number, since it is larger than the sum of its proper divisors (1).

815681681 is an equidigital number, since it uses as much as digits as its factorization.

815681681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 92160, while the sum is 44.

The square root of 815681681 is about 28560.1414737392. The cubic root of 815681681 is about 934.3442191640.

The spelling of 815681681 in words is "eight hundred fifteen million, six hundred eighty-one thousand, six hundred eighty-one".