81580257 has 24 divisors (see below), whose sum is σ = 132851040. Its totient is φ = 49440600.

The previous prime is 81580217. The next prime is 81580273. The reversal of 81580257 is 75208518.

It is not a de Polignac number, because 81580257 - 2¹⁸ = 81318113 is a prime.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (81580217) 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 in 23 ways as a sum of consecutive naturals, for example, 9219 + ... + 15752.

It is an arithmetic number, because the mean of its divisors is an integer number (5535460).

Almost surely, 2^81580257 is an apocalyptic number.

It is an amenable number.

81580257 is a deficient number, since it is larger than the sum of its proper divisors (51270783).

81580257 is a wasteful number, since it uses less digits than its factorization.

81580257 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25002 (or 24985 counting only the distinct ones).

The product of its (nonzero) digits is 22400, while the sum is 36.

The square root of 81580257 is about 9032.1789729832. The cubic root of 81580257 is about 433.7055932635.

The spelling of 81580257 in words is "eighty-one million, five hundred eighty thousand, two hundred fifty-seven".