81138193 has 8 divisors (see below), whose sum is σ = 81936360. Its totient is φ = 80344320.

The previous prime is 81138179. The next prime is 81138223. The reversal of 81138193 is 39183118.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 31899904 + 49238289 = 5648^2 + 7017^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81138193 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81138103) 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, 46623 + ... + 48331.

It is an arithmetic number, because the mean of its divisors is an integer number (10242045).

Almost surely, 2^81138193 is an apocalyptic number.

It is an amenable number.

81138193 is a deficient number, since it is larger than the sum of its proper divisors (798167).

81138193 is a wasteful number, since it uses less digits than its factorization.

81138193 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2147.

The product of its digits is 5184, while the sum is 34.

The square root of 81138193 is about 9007.6741171070. The cubic root of 81138193 is about 432.9207915319.

The spelling of 81138193 in words is "eighty-one million, one hundred thirty-eight thousand, one hundred ninety-three".