81355091 has 4 divisors (see below), whose sum is σ = 81385512. Its totient is φ = 81324672.

The previous prime is 81355037. The next prime is 81355133. The reversal of 81355091 is 19055318.

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 81355091 - 2²⁶ = 14246227 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81355291) 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, 10766 + ... + 16691.

It is an arithmetic number, because the mean of its divisors is an integer number (20346378).

Almost surely, 2^81355091 is an apocalyptic number.

81355091 is a deficient number, since it is larger than the sum of its proper divisors (30421).

81355091 is a wasteful number, since it uses less digits than its factorization.

81355091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30420.

The product of its (nonzero) digits is 5400, while the sum is 32.

The square root of 81355091 is about 9019.7057047334. The cubic root of 81355091 is about 433.3062084928.

The spelling of 81355091 in words is "eighty-one million, three hundred fifty-five thousand, ninety-one".