81605730 has 16 divisors (see below), whose sum is σ = 195853824. Its totient is φ = 21761520.

The previous prime is 81605717. The next prime is 81605731. The reversal of 81605730 is 3750618.

It is a Harshad number since it is a multiple of its sum of digits (30), and also a Moran number because the ratio is a prime number: 2720191 = 81605730 / (8 + 1 + 6 + 0 + 5 + 7 + 3 + 0).

It is not an unprimeable number, because it can be changed into a prime (81605731) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 1360066 + ... + 1360125.

It is an arithmetic number, because the mean of its divisors is an integer number (12240864).

Almost surely, 2^81605730 is an apocalyptic number.

81605730 is an abundant number, since it is smaller than the sum of its proper divisors (114248094).

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

81605730 is a wasteful number, since it uses less digits than its factorization.

81605730 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2720201.

The product of its (nonzero) digits is 5040, while the sum is 30.

The square root of 81605730 is about 9033.5889877722. The cubic root of 81605730 is about 433.7507293186.

The spelling of 81605730 in words is "eighty-one million, six hundred five thousand, seven hundred thirty".