81159805440 has 960 divisors, whose sum is σ = 346619243520. Its totient is φ = 17929175040.

The previous prime is 81159805429. The next prime is 81159805459. The reversal of 81159805440 is 4450895118.

It is a happy number.

81159805440 is a `hidden beast` number, since 8 + 1 + 1 + 598 + 0 + 54 + 4 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (960).

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, 104992894 + ... + 104993666.

It is an arithmetic number, because the mean of its divisors is an integer number (361061712).

Almost surely, 2^81159805440 is an apocalyptic number.

81159805440 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 81159805440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (173309621760).

81159805440 is an abundant number, since it is smaller than the sum of its proper divisors (265459438080).

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

81159805440 is a wasteful number, since it uses less digits than its factorization.

81159805440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 850 (or 821 counting only the distinct ones).

The product of its (nonzero) digits is 230400, while the sum is 45.

The spelling of 81159805440 in words is "eighty-one billion, one hundred fifty-nine million, eight hundred five thousand, four hundred forty".