81381544091 has 4 divisors (see below), whose sum is σ = 82002777384. Its totient is φ = 80760310800.

The previous prime is 81381544081. The next prime is 81381544103. The reversal of 81381544091 is 19044518318.

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 81381544091 - 2²² = 81377349787 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81381544001) 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, 310616450 + ... + 310616711.

It is an arithmetic number, because the mean of its divisors is an integer number (20500694346).

Almost surely, 2^81381544091 is an apocalyptic number.

81381544091 is a deficient number, since it is larger than the sum of its proper divisors (621233293).

81381544091 is a wasteful number, since it uses less digits than its factorization.

81381544091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 621233292.

The product of its (nonzero) digits is 138240, while the sum is 44.

The spelling of 81381544091 in words is "eighty-one billion, three hundred eighty-one million, five hundred forty-four thousand, ninety-one".