81089720 has 64 divisors (see below), whose sum is σ = 200448000. Its totient is φ = 29386368.

The previous prime is 81089699. The next prime is 81089747. The reversal of 81089720 is 2798018.

It is a happy number.

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, 15161 + ... + 19799.

It is an arithmetic number, because the mean of its divisors is an integer number (3132000).

Almost surely, 2^81089720 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 81089720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (100224000).

81089720 is an abundant number, since it is smaller than the sum of its proper divisors (119358280).

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

81089720 is a wasteful number, since it uses less digits than its factorization.

81089720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4692 (or 4688 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 35.

The square root of 81089720 is about 9004.9830649480. The cubic root of 81089720 is about 432.8345635422.

The spelling of 81089720 in words is "eighty-one million, eighty-nine thousand, seven hundred twenty".