81585780 has 48 divisors (see below), whose sum is σ = 230719104. Its totient is φ = 21539200.

The previous prime is 81585767. The next prime is 81585781. The reversal of 81585780 is 8758518.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81585781) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 672 + ... + 12791.

It is an arithmetic number, because the mean of its divisors is an integer number (4806648).

Almost surely, 2^81585780 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 81585780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (115359552).

81585780 is an abundant number, since it is smaller than the sum of its proper divisors (149133324).

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

81585780 is a wasteful number, since it uses less digits than its factorization.

81585780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13576 (or 13574 counting only the distinct ones).

The product of its (nonzero) digits is 89600, while the sum is 42.

The square root of 81585780 is about 9032.4847079859. The cubic root of 81585780 is about 433.7153803617.

The spelling of 81585780 in words is "eighty-one million, five hundred eighty-five thousand, seven hundred eighty".