81393617 has 4 divisors (see below), whose sum is σ = 81683556. Its totient is φ = 81103680.

The previous prime is 81393607. The next prime is 81393623. The reversal of 81393617 is 71639318.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 71639318 = 2 ⋅35819659.

It can be written as a sum of positive squares in 2 ways, for example, as 38241856 + 43151761 = 6184^2 + 6569^2 .

It is a cyclic number.

It is not a de Polignac number, because 81393617 - 2⁶ = 81393553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81393607) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 144548 + ... + 145109.

It is an arithmetic number, because the mean of its divisors is an integer number (20420889).

Almost surely, 2^81393617 is an apocalyptic number.

It is an amenable number.

81393617 is a deficient number, since it is larger than the sum of its proper divisors (289939).

81393617 is a wasteful number, since it uses less digits than its factorization.

81393617 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 289938.

The product of its digits is 27216, while the sum is 38.

The square root of 81393617 is about 9021.8411092193. The cubic root of 81393617 is about 433.3745956106.

The spelling of 81393617 in words is "eighty-one million, three hundred ninety-three thousand, six hundred seventeen".