81611320 has 64 divisors (see below), whose sum is σ = 215006400. Its totient is φ = 27294720.

The previous prime is 81611303. The next prime is 81611353. The reversal of 81611320 is 2311618.

It is a junction number, because it is equal to n+sod(n) for n = 81611291 and 81611300.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7926 + ... + 15034.

It is an arithmetic number, because the mean of its divisors is an integer number (3359475).

Almost surely, 2^81611320 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81611320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (107503200).

81611320 is an abundant number, since it is smaller than the sum of its proper divisors (133395080).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81611320 is a wasteful number, since it uses less digits than its factorization.

81611320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7168 (or 7164 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 22.

The square root of 81611320 is about 9033.8983833116. The cubic root of 81611320 is about 433.7606330807.

Adding to 81611320 its reverse (2311618), we get a palindrome (83922938).

The spelling of 81611320 in words is "eighty-one million, six hundred eleven thousand, three hundred twenty".