81506638528 has 112 divisors (see below), whose sum is σ = 187200584704. Its totient is φ = 34488115200.

The previous prime is 81506638517. The next prime is 81506638537. The reversal of 81506638528 is 82583660518.

It is a tau number, because it is divible by the number of its divisors (112).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 20118103 + ... + 20122153.

It is an arithmetic number, because the mean of its divisors is an integer number (1671433792).

Almost surely, 2^81506638528 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 81506638528, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (93600292352).

81506638528 is an abundant number, since it is smaller than the sum of its proper divisors (105693946176).

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

81506638528 is a wasteful number, since it uses less digits than its factorization.

81506638528 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4630 (or 4620 counting only the distinct ones).

The product of its (nonzero) digits is 2764800, while the sum is 52.

The spelling of 81506638528 in words is "eighty-one billion, five hundred six million, six hundred thirty-eight thousand, five hundred twenty-eight".