81396491 has 16 divisors (see below), whose sum is σ = 90771840. Its totient is φ = 72367680.

The previous prime is 81396473. The next prime is 81396503. The reversal of 81396491 is 19469318.

It is a de Polignac number, because none of the positive numbers 2^k-81396491 is a prime.

It is a super-2 number, since 2×81396491² = 13250777494226162, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81396431) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 131615 + ... + 132231.

It is an arithmetic number, because the mean of its divisors is an integer number (5673240).

Almost surely, 2^81396491 is an apocalyptic number.

81396491 is a deficient number, since it is larger than the sum of its proper divisors (9375349).

81396491 is a wasteful number, since it uses less digits than its factorization.

81396491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 874.

The product of its digits is 46656, while the sum is 41.

The square root of 81396491 is about 9022.0003879406. Note that the first 3 decimals coincide. The cubic root of 81396491 is about 433.3796963543.

The spelling of 81396491 in words is "eighty-one million, three hundred ninety-six thousand, four hundred ninety-one".