81138219 has 4 divisors (see below), whose sum is σ = 108184296. Its totient is φ = 54092144.

The previous prime is 81138179. The next prime is 81138223. The reversal of 81138219 is 91283118.

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 81138219 - 2⁷ = 81138091 is a prime.

It is a super-2 number, since 2×81138219² = 13166821164983922, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81138219.

It is not an unprimeable number, because it can be changed into a prime (81138419) 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, 13523034 + ... + 13523039.

It is an arithmetic number, because the mean of its divisors is an integer number (27046074).

Almost surely, 2^81138219 is an apocalyptic number.

81138219 is a deficient number, since it is larger than the sum of its proper divisors (27046077).

81138219 is a wasteful number, since it uses less digits than its factorization.

81138219 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27046076.

The product of its digits is 3456, while the sum is 33.

The square root of 81138219 is about 9007.6755603208. The cubic root of 81138219 is about 432.9208377738.

The spelling of 81138219 in words is "eighty-one million, one hundred thirty-eight thousand, two hundred nineteen".