81520389504 has 384 divisors, whose sum is σ = 256374144000. Its totient is φ = 24768737280.

The previous prime is 81520389499. The next prime is 81520389541. The reversal of 81520389504 is 40598302518.

81520389504 is a `hidden beast` number, since 8 + 1 + 520 + 38 + 95 + 0 + 4 = 666.

It is a tau number, because it is divible by the number of its divisors (384).

It is a self number, because there is not a number n which added to its sum of digits gives 81520389504.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 215093187 + ... + 215093565.

It is an arithmetic number, because the mean of its divisors is an integer number (667641000).

Almost surely, 2^81520389504 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 81520389504, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (128187072000).

81520389504 is an abundant number, since it is smaller than the sum of its proper divisors (174853754496).

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

81520389504 is a wasteful number, since it uses less digits than its factorization.

81520389504 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 766 (or 751 counting only the distinct ones).

The product of its (nonzero) digits is 345600, while the sum is 45.

The spelling of 81520389504 in words is "eighty-one billion, five hundred twenty million, three hundred eighty-nine thousand, five hundred four".