81933191 has 4 divisors (see below), whose sum is σ = 82970400. Its totient is φ = 80895984.

The previous prime is 81933169. The next prime is 81933197. The reversal of 81933191 is 19133918.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81933191 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 (81933197) 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, 518486 + ... + 518643.

It is an arithmetic number, because the mean of its divisors is an integer number (20742600).

Almost surely, 2^81933191 is an apocalyptic number.

81933191 is a deficient number, since it is larger than the sum of its proper divisors (1037209).

81933191 is a wasteful number, since it uses less digits than its factorization.

81933191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1037208.

The product of its digits is 5832, while the sum is 35.

The square root of 81933191 is about 9051.6954765392. The cubic root of 81933191 is about 434.3301285257.

The spelling of 81933191 in words is "eighty-one million, nine hundred thirty-three thousand, one hundred ninety-one".