81011111 has 4 divisors (see below), whose sum is σ = 82339224. Its totient is φ = 79683000.

The previous prime is 81011081. The next prime is 81011113. The reversal of 81011111 is 11111018.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 11111018 = 2 ⋅5555509.

It is a cyclic number.

It is not a de Polignac number, because 81011111 - 2¹⁰ = 81010087 is a prime.

It is a Duffinian number.

81011111 is a modest number, since divided by 11111 gives 810 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81011113) 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, 663965 + ... + 664086.

It is an arithmetic number, because the mean of its divisors is an integer number (20584806).

Almost surely, 2^81011111 is an apocalyptic number.

81011111 is a deficient number, since it is larger than the sum of its proper divisors (1328113).

81011111 is a wasteful number, since it uses less digits than its factorization.

81011111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1328112.

The product of its (nonzero) digits is 8, while the sum is 14.

The square root of 81011111 is about 9000.6172566108. The cubic root of 81011111 is about 432.6946539346.

Adding to 81011111 its reverse (11111018), we get a palindrome (92122129).

The spelling of 81011111 in words is "eighty-one million, eleven thousand, one hundred eleven".