81591743 has 4 divisors (see below), whose sum is σ = 81618768. Its totient is φ = 81564720.

The previous prime is 81591733. The next prime is 81591779. The reversal of 81591743 is 34719518.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 34719518 = 2 ⋅17359759.

It is a cyclic number.

It is not a de Polignac number, because 81591743 - 2¹⁴ = 81575359 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81591697 and 81591706.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81591733) 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, 8318 + ... + 15243.

It is an arithmetic number, because the mean of its divisors is an integer number (20404692).

Almost surely, 2^81591743 is an apocalyptic number.

81591743 is a deficient number, since it is larger than the sum of its proper divisors (27025).

81591743 is a wasteful number, since it uses less digits than its factorization.

81591743 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27024.

The product of its digits is 30240, while the sum is 38.

The square root of 81591743 is about 9032.8147883149. The cubic root of 81591743 is about 433.7259466712.

The spelling of 81591743 in words is "eighty-one million, five hundred ninety-one thousand, seven hundred forty-three".