81398381 has 4 divisors (see below), whose sum is σ = 81739200. Its totient is φ = 81057564.

The previous prime is 81398353. The next prime is 81398393. The reversal of 81398381 is 18389318.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 18389318 = 2 ⋅9194659.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81398381 is a prime.

It is a super-2 number, since 2×81398381² = 13251392858842322, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81398881) 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, 170051 + ... + 170528.

It is an arithmetic number, because the mean of its divisors is an integer number (20434800).

Almost surely, 2^81398381 is an apocalyptic number.

It is an amenable number.

81398381 is a deficient number, since it is larger than the sum of its proper divisors (340819).

81398381 is a wasteful number, since it uses less digits than its factorization.

81398381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 340818.

The product of its digits is 41472, while the sum is 41.

The square root of 81398381 is about 9022.1051312873. The cubic root of 81398381 is about 433.3830506401.

The spelling of 81398381 in words is "eighty-one million, three hundred ninety-eight thousand, three hundred eighty-one".