81138399 has 8 divisors (see below), whose sum is σ = 114548400. Its totient is φ = 50910336.

The previous prime is 81138383. The next prime is 81138413. The reversal of 81138399 is 99383118.

It is a happy number.

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

It is not a de Polignac number, because 81138399 - 2⁴ = 81138383 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81138399.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81138599) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 795424 + ... + 795525.

It is an arithmetic number, because the mean of its divisors is an integer number (14318550).

Almost surely, 2^81138399 is an apocalyptic number.

81138399 is a deficient number, since it is larger than the sum of its proper divisors (33410001).

81138399 is a wasteful number, since it uses less digits than its factorization.

81138399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1590969.

The product of its digits is 46656, while the sum is 42.

The square root of 81138399 is about 9007.6855517941. The cubic root of 81138399 is about 432.9211579094.

The spelling of 81138399 in words is "eighty-one million, one hundred thirty-eight thousand, three hundred ninety-nine".