81191113 has 4 divisors (see below), whose sum is σ = 81384388. Its totient is φ = 80997840.

The previous prime is 81191107. The next prime is 81191119. The reversal of 81191113 is 31119118.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 31119118 = 2 ⋅15559559.

It is an interprime number because it is at equal distance from previous prime (81191107) and next prime (81191119).

It can be written as a sum of positive squares in 2 ways, for example, as 22024249 + 59166864 = 4693^2 + 7692^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81191113 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81191119) 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, 96006 + ... + 96847.

It is an arithmetic number, because the mean of its divisors is an integer number (20346097).

Almost surely, 2^81191113 is an apocalyptic number.

It is an amenable number.

81191113 is a deficient number, since it is larger than the sum of its proper divisors (193275).

81191113 is a wasteful number, since it uses less digits than its factorization.

81191113 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 193274.

The product of its digits is 216, while the sum is 25.

The square root of 81191113 is about 9010.6111335469. The cubic root of 81191113 is about 433.0148910282.

The spelling of 81191113 in words is "eighty-one million, one hundred ninety-one thousand, one hundred thirteen".