81281391 has 8 divisors (see below), whose sum is σ = 108635520. Its totient is φ = 54057432.

The previous prime is 81281381. The next prime is 81281399. The reversal of 81281391 is 19318218.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81281391 - 2⁶ = 81281327 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81281399) 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 7 ways as a sum of consecutive naturals, for example, 31075 + ... + 33588.

It is an arithmetic number, because the mean of its divisors is an integer number (13579440).

Almost surely, 2^81281391 is an apocalyptic number.

81281391 is a deficient number, since it is larger than the sum of its proper divisors (27354129).

81281391 is a wasteful number, since it uses less digits than its factorization.

81281391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 65085.

The product of its digits is 3456, while the sum is 33.

The square root of 81281391 is about 9015.6192798942. The cubic root of 81281391 is about 433.1753241794.

The spelling of 81281391 in words is "eighty-one million, two hundred eighty-one thousand, three hundred ninety-one".