81381827520 has 1568 divisors, whose sum is σ = 363529351680. Its totient is φ = 16930529280.

The previous prime is 81381827519. The next prime is 81381827537. The reversal of 81381827520 is 2572818318.

81381827520 is a `hidden beast` number, since 81 + 38 + 18 + 2 + 7 + 520 = 666.

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

It is a congruent number.

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 223 ways as a sum of consecutive naturals, for example, 1334128290 + ... + 1334128350.

Almost surely, 2^81381827520 is an apocalyptic number.

81381827520 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 81381827520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (181764675840).

81381827520 is an abundant number, since it is smaller than the sum of its proper divisors (282147524160).

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

81381827520 is a wasteful number, since it uses less digits than its factorization.

81381827520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 165 (or 140 counting only the distinct ones).

The product of its (nonzero) digits is 215040, while the sum is 45.

The spelling of 81381827520 in words is "eighty-one billion, three hundred eighty-one million, eight hundred twenty-seven thousand, five hundred twenty".