81199117 has 4 divisors (see below), whose sum is σ = 81420736. Its totient is φ = 80977500.

The previous prime is 81199099. The next prime is 81199133. The reversal of 81199117 is 71199118.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81199117 - 2¹⁹ = 80674829 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81199187) 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, 110259 + ... + 110992.

It is an arithmetic number, because the mean of its divisors is an integer number (20355184).

Almost surely, 2^81199117 is an apocalyptic number.

It is an amenable number.

81199117 is a deficient number, since it is larger than the sum of its proper divisors (221619).

81199117 is a wasteful number, since it uses less digits than its factorization.

81199117 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 221618.

The product of its digits is 4536, while the sum is 37.

The square root of 81199117 is about 9011.0552656168. The cubic root of 81199117 is about 433.0291197501.

Subtracting from 81199117 its reverse (71199118), we obtain a palindrome (9999999).

The spelling of 81199117 in words is "eighty-one million, one hundred ninety-nine thousand, one hundred seventeen".