81138047 has 4 divisors (see below), whose sum is σ = 81941496. Its totient is φ = 80334600.

The previous prime is 81138023. The next prime is 81138049. The reversal of 81138047 is 74083118.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81138047 - 2⁶ = 81137983 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81138049) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 401573 + ... + 401774.

It is an arithmetic number, because the mean of its divisors is an integer number (20485374).

Almost surely, 2^81138047 is an apocalyptic number.

81138047 is a deficient number, since it is larger than the sum of its proper divisors (803449).

81138047 is a wasteful number, since it uses less digits than its factorization.

81138047 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 803448.

The product of its (nonzero) digits is 5376, while the sum is 32.

The square root of 81138047 is about 9007.6660129026. Note that the first 3 decimals coincide. The cubic root of 81138047 is about 432.9205318660.

The spelling of 81138047 in words is "eighty-one million, one hundred thirty-eight thousand, forty-seven".