81312577 has 2 divisors, whose sum is σ = 81312578. Its totient is φ = 81312576.

The previous prime is 81312559. The next prime is 81312587. The reversal of 81312577 is 77521318.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 79014321 + 2298256 = 8889^2 + 1516^2 .

It is a cyclic number.

It is not a de Polignac number, because 81312577 - 2¹⁹ = 80788289 is a prime.

It is a super-2 number, since 2×81312577² = 13223470356761858, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81312557) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40656288 + 40656289.

It is an arithmetic number, because the mean of its divisors is an integer number (40656289).

Almost surely, 2^81312577 is an apocalyptic number.

It is an amenable number.

81312577 is a deficient number, since it is larger than the sum of its proper divisors (1).

81312577 is an equidigital number, since it uses as much as digits as its factorization.

81312577 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 11760, while the sum is 34.

The square root of 81312577 is about 9017.3486679844. The cubic root of 81312577 is about 433.2307172534.

The spelling of 81312577 in words is "eighty-one million, three hundred twelve thousand, five hundred seventy-seven".