81445587720 has 256 divisors, whose sum is σ = 296061696000. Its totient is φ = 17508980736.

The previous prime is 81445587697. The next prime is 81445587749. The reversal of 81445587720 is 2778554418.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 2200084 + ... + 2236796.

It is an arithmetic number, because the mean of its divisors is an integer number (1156491000).

Almost surely, 2^81445587720 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 81445587720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (148030848000).

81445587720 is an abundant number, since it is smaller than the sum of its proper divisors (214616108280).

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

81445587720 is a wasteful number, since it uses less digits than its factorization.

81445587720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36892 (or 36888 counting only the distinct ones).

The product of its (nonzero) digits is 2508800, while the sum is 51.

The spelling of 81445587720 in words is "eighty-one billion, four hundred forty-five million, five hundred eighty-seven thousand, seven hundred twenty".