81831109 has 4 divisors (see below), whose sum is σ = 82641420. Its totient is φ = 81020800.

The previous prime is 81831067. The next prime is 81831133. The reversal of 81831109 is 90113818.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 40678884 + 41152225 = 6378^2 + 6415^2 .

It is a cyclic number.

It is not a de Polignac number, because 81831109 - 2⁹ = 81830597 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 (81831179) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 405004 + ... + 405205.

It is an arithmetic number, because the mean of its divisors is an integer number (20660355).

Almost surely, 2^81831109 is an apocalyptic number.

It is an amenable number.

81831109 is a deficient number, since it is larger than the sum of its proper divisors (810311).

81831109 is a wasteful number, since it uses less digits than its factorization.

81831109 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 810310.

The product of its (nonzero) digits is 1728, while the sum is 31.

The square root of 81831109 is about 9046.0548859710. The cubic root of 81831109 is about 434.1496737188.

The spelling of 81831109 in words is "eighty-one million, eight hundred thirty-one thousand, one hundred nine".