81159780 has 96 divisors (see below), whose sum is σ = 248540544. Its totient is φ = 19666944.

The previous prime is 81159779. The next prime is 81159839. The reversal of 81159780 is 8795118.

81159780 is digitally balanced in base 9, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (39).

81159780 is strictly pandigital in base 9.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 51484 + ... + 53036.

It is an arithmetic number, because the mean of its divisors is an integer number (2588964).

Almost surely, 2^81159780 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 81159780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (124270272).

81159780 is an abundant number, since it is smaller than the sum of its proper divisors (167380764).

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

81159780 is a wasteful number, since it uses less digits than its factorization.

81159780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1645 (or 1643 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 39.

The square root of 81159780 is about 9008.8722934671. The cubic root of 81159780 is about 432.9591813132.

The spelling of 81159780 in words is "eighty-one million, one hundred fifty-nine thousand, seven hundred eighty".