81815438 has 16 divisors (see below), whose sum is σ = 129660480. Its totient is φ = 38655456.

The previous prime is 81815431. The next prime is 81815443. The reversal of 81815438 is 83451818.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81815431) 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, 12281 + ... + 17732.

It is an arithmetic number, because the mean of its divisors is an integer number (8103780).

Almost surely, 2^81815438 is an apocalyptic number.

81815438 is a deficient number, since it is larger than the sum of its proper divisors (47845042).

81815438 is a wasteful number, since it uses less digits than its factorization.

81815438 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30091.

The product of its digits is 30720, while the sum is 38.

The square root of 81815438 is about 9045.1886658046. The cubic root of 81815438 is about 434.1219581228.

The spelling of 81815438 in words is "eighty-one million, eight hundred fifteen thousand, four hundred thirty-eight".