81585065309 has 4 divisors (see below), whose sum is σ = 89001889440. Its totient is φ = 74168241180.

The previous prime is 81585065251. The next prime is 81585065357. The reversal of 81585065309 is 90356058518.

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 not a de Polignac number, because 81585065309 - 2¹² = 81585061213 is a prime.

It is a super-2 number, since 2×81585065309² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81585065399) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3708412049 + ... + 3708412070.

It is an arithmetic number, because the mean of its divisors is an integer number (22250472360).

Almost surely, 2^81585065309 is an apocalyptic number.

It is an amenable number.

81585065309 is a deficient number, since it is larger than the sum of its proper divisors (7416824131).

81585065309 is a wasteful number, since it uses less digits than its factorization.

81585065309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7416824130.

The product of its (nonzero) digits is 1296000, while the sum is 50.

The spelling of 81585065309 in words is "eighty-one billion, five hundred eighty-five million, sixty-five thousand, three hundred nine".