81289320 has 256 divisors, whose sum is σ = 298598400. Its totient is φ = 17310720.

The previous prime is 81289309. The next prime is 81289339. The reversal of 81289320 is 2398218.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1144885 + ... + 1144955.

It is an arithmetic number, because the mean of its divisors is an integer number (1166400).

Almost surely, 2^81289320 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 81289320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (149299200).

81289320 is an abundant number, since it is smaller than the sum of its proper divisors (217309080).

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

81289320 is a wasteful number, since it uses less digits than its factorization.

81289320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 168 (or 164 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 33.

The square root of 81289320 is about 9016.0590060181. The cubic root of 81289320 is about 433.1894091396.

The spelling of 81289320 in words is "eighty-one million, two hundred eighty-nine thousand, three hundred twenty".