81408733520 has 80 divisors (see below), whose sum is σ = 193353910272. Its totient is φ = 31865034240.

The previous prime is 81408733507. The next prime is 81408733531. The reversal of 81408733520 is 2533780418.

It is a tau number, because it is divible by the number of its divisors (80).

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 15 ways as a sum of consecutive naturals, for example, 1598855 + ... + 1648985.

Almost surely, 2^81408733520 is an apocalyptic number.

81408733520 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 81408733520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (96676955136).

81408733520 is an abundant number, since it is smaller than the sum of its proper divisors (111945176752).

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

81408733520 is a wasteful number, since it uses less digits than its factorization.

81408733520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50580 (or 50574 counting only the distinct ones).

The product of its (nonzero) digits is 161280, while the sum is 41.

The spelling of 81408733520 in words is "eighty-one billion, four hundred eight million, seven hundred thirty-three thousand, five hundred twenty".