81322320 has 80 divisors (see below), whose sum is σ = 253733760. Its totient is φ = 21545472.

The previous prime is 81322313. The next prime is 81322357. The reversal of 81322320 is 2322318.

It is a tau number, because it is divible by the number of its divisors (80).

It is a super-2 number, since 2×81322320² = 13226639460364800, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 39066 + ... + 41094.

It is an arithmetic number, because the mean of its divisors is an integer number (3171672).

Almost surely, 2^81322320 is an apocalyptic number.

81322320 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81322320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (126866880).

81322320 is an abundant number, since it is smaller than the sum of its proper divisors (172411440).

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

81322320 is a wasteful number, since it uses less digits than its factorization.

81322320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2212 (or 2206 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 21.

The square root of 81322320 is about 9017.8888882044. Note that the first 6 decimals coincide. The cubic root of 81322320 is about 433.2480200228.

Adding to 81322320 its reverse (2322318), we get a palindrome (83644638).

The spelling of 81322320 in words is "eighty-one million, three hundred twenty-two thousand, three hundred twenty".