81936791 has 4 divisors (see below), whose sum is σ = 81956184. Its totient is φ = 81917400.

The previous prime is 81936749. The next prime is 81936793. The reversal of 81936791 is 19763918.

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

It is a cyclic number.

It is not a de Polignac number, because 81936791 - 2¹⁴ = 81920407 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 (81936793) 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, 365 + ... + 12806.

It is an arithmetic number, because the mean of its divisors is an integer number (20489046).

Almost surely, 2^81936791 is an apocalyptic number.

81936791 is a deficient number, since it is larger than the sum of its proper divisors (19393).

81936791 is a wasteful number, since it uses less digits than its factorization.

81936791 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19392.

The product of its digits is 81648, while the sum is 44.

The square root of 81936791 is about 9051.8943321274. The cubic root of 81936791 is about 434.3364896660.

The spelling of 81936791 in words is "eighty-one million, nine hundred thirty-six thousand, seven hundred ninety-one".