81578113 has 4 divisors (see below), whose sum is σ = 81665748. Its totient is φ = 81490480.

The previous prime is 81578111. The next prime is 81578141. The reversal of 81578113 is 31187518.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 50296464 + 31281649 = 7092^2 + 5593^2 .

It is a cyclic number.

It is not a de Polignac number, because 81578113 - 2¹ = 81578111 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81578111) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 42406 + ... + 44287.

It is an arithmetic number, because the mean of its divisors is an integer number (20416437).

Almost surely, 2^81578113 is an apocalyptic number.

It is an amenable number.

81578113 is a deficient number, since it is larger than the sum of its proper divisors (87635).

81578113 is an equidigital number, since it uses as much as digits as its factorization.

81578113 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 87634.

The product of its digits is 6720, while the sum is 34.

The square root of 81578113 is about 9032.0602854498. The cubic root of 81578113 is about 433.7017938437.

The spelling of 81578113 in words is "eighty-one million, five hundred seventy-eight thousand, one hundred thirteen".