81138615 has 8 divisors (see below), whose sum is σ = 129821808. Its totient is φ = 43273920.

The previous prime is 81138611. The next prime is 81138623. The reversal of 81138615 is 51683118.

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

It is not a de Polignac number, because 81138615 - 2² = 81138611 is a prime.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81138611) 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, 2704606 + ... + 2704635.

It is an arithmetic number, because the mean of its divisors is an integer number (16227726).

Almost surely, 2^81138615 is an apocalyptic number.

81138615 is a deficient number, since it is larger than the sum of its proper divisors (48683193).

81138615 is a wasteful number, since it uses less digits than its factorization.

81138615 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5409249.

The product of its digits is 5760, while the sum is 33.

The square root of 81138615 is about 9007.6975415475. The cubic root of 81138615 is about 432.9215420714.

The spelling of 81138615 in words is "eighty-one million, one hundred thirty-eight thousand, six hundred fifteen".