81138305 has 8 divisors (see below), whose sum is σ = 97579944. Its totient is φ = 64768000.

The previous prime is 81138301. The next prime is 81138307. The reversal of 81138305 is 50383118.

It can be written as a sum of positive squares in 4 ways, for example, as 5726449 + 75411856 = 2393^2 + 8684^2 .

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

It is not a de Polignac number, because 81138305 - 2² = 81138301 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81138301) 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, 15296 + ... + 19905.

It is an arithmetic number, because the mean of its divisors is an integer number (12197493).

Almost surely, 2^81138305 is an apocalyptic number.

It is an amenable number.

81138305 is a deficient number, since it is larger than the sum of its proper divisors (16441639).

81138305 is a wasteful number, since it uses less digits than its factorization.

81138305 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35667.

The product of its (nonzero) digits is 2880, while the sum is 29.

The square root of 81138305 is about 9007.6803340261. The cubic root of 81138305 is about 432.9209907275.

The spelling of 81138305 in words is "eighty-one million, one hundred thirty-eight thousand, three hundred five".