81199118 has 32 divisors (see below), whose sum is σ = 163537920.
Its totient is φ = 29201760.
The previous prime is 81199099. The next prime is 81199133.
81199118 is nontrivially palindromic in base 10.
It is a Smith number, since the sum of its digits (38) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.
It is a congruent number.
It is an unprimeable number.
It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 18278 + ... + 22281.
It is an arithmetic number, because the mean of its divisors is an integer number (5110560).
Almost surely, 281199118 is an apocalyptic number.
81199118 is an abundant number, since it is smaller than the sum of its proper divisors (82338802).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
81199118 is a wasteful number, since it uses less digits than its factorization.
81199118 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 40592.
The product of its digits is 5184, while the sum is 38.
The square root of 81199118 is about 9011.0553211042.
The cubic root of 81199118 is about 433.0291215277.
The spelling of 81199118 in words is "eighty-one million, one hundred ninety-nine thousand, one hundred eighteen".