81505793 has 4 divisors (see below), whose sum is σ = 81540528. Its totient is φ = 81471060.

The previous prime is 81505777. The next prime is 81505807. The reversal of 81505793 is 39750518.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81505793 - 2⁴ = 81505777 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81505393) 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 3 ways as a sum of consecutive naturals, for example, 13571 + ... + 18632.

It is an arithmetic number, because the mean of its divisors is an integer number (20385132).

Almost surely, 2^81505793 is an apocalyptic number.

It is an amenable number.

81505793 is a deficient number, since it is larger than the sum of its proper divisors (34735).

81505793 is a wasteful number, since it uses less digits than its factorization.

81505793 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34734.

The product of its (nonzero) digits is 37800, while the sum is 38.

The square root of 81505793 is about 9028.0558815284. The cubic root of 81505793 is about 433.5735952958.

The spelling of 81505793 in words is "eighty-one million, five hundred five thousand, seven hundred ninety-three".