81940791 has 4 divisors (see below), whose sum is σ = 109254392. Its totient is φ = 54627192.

The previous prime is 81940783. The next prime is 81940801. The reversal of 81940791 is 19704918.

It is a happy number.

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

It is not a de Polignac number, because 81940791 - 2³ = 81940783 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81920791) 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, 13656796 + ... + 13656801.

It is an arithmetic number, because the mean of its divisors is an integer number (27313598).

Almost surely, 2^81940791 is an apocalyptic number.

81940791 is a deficient number, since it is larger than the sum of its proper divisors (27313601).

81940791 is a wasteful number, since it uses less digits than its factorization.

81940791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27313600.

The product of its (nonzero) digits is 18144, while the sum is 39.

The square root of 81940791 is about 9052.1152776575. The cubic root of 81940791 is about 434.3435573811.

The spelling of 81940791 in words is "eighty-one million, nine hundred forty thousand, seven hundred ninety-one".