81585813 has 4 divisors (see below), whose sum is σ = 108781088. Its totient is φ = 54390540.

The previous prime is 81585811. The next prime is 81585857. The reversal of 81585813 is 31858518.

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 81585813 - 2¹ = 81585811 is a prime.

It is a super-3 number, since 3×81585813³ (a number of 25 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81585811) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13597633 + ... + 13597638.

It is an arithmetic number, because the mean of its divisors is an integer number (27195272).

Almost surely, 2^81585813 is an apocalyptic number.

It is an amenable number.

81585813 is a deficient number, since it is larger than the sum of its proper divisors (27195275).

81585813 is a wasteful number, since it uses less digits than its factorization.

81585813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27195274.

The product of its digits is 38400, while the sum is 39.

The square root of 81585813 is about 9032.4865347256. The cubic root of 81585813 is about 433.7154388384.

The spelling of 81585813 in words is "eighty-one million, five hundred eighty-five thousand, eight hundred thirteen".