81527281920 has 864 divisors, whose sum is σ = 347622589440. Its totient is φ = 18022072320.

The previous prime is 81527281909. The next prime is 81527281949. The reversal of 81527281920 is 2918272518.

81527281920 is a `hidden beast` number, since 81 + 527 + 28 + 1 + 9 + 20 = 666.

It is a tau number, because it is divible by the number of its divisors (864).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 52495864 + ... + 52497416.

It is an arithmetic number, because the mean of its divisors is an integer number (402340960).

Almost surely, 2^81527281920 is an apocalyptic number.

81527281920 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 81527281920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (173811294720).

81527281920 is an abundant number, since it is smaller than the sum of its proper divisors (266095307520).

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

81527281920 is a wasteful number, since it uses less digits than its factorization.

81527281920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1628 (or 1601 counting only the distinct ones).

The product of its (nonzero) digits is 161280, while the sum is 45.

The spelling of 81527281920 in words is "eighty-one billion, five hundred twenty-seven million, two hundred eighty-one thousand, nine hundred twenty".