81671728 has 80 divisors (see below), whose sum is σ = 175569120. Its totient is φ = 36661248.

The previous prime is 81671683. The next prime is 81671729. The reversal of 81671728 is 82717618.

It is not an unprimeable number, because it can be changed into a prime (81671729) 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 15 ways as a sum of consecutive naturals, for example, 596076 + ... + 596212.

It is an arithmetic number, because the mean of its divisors is an integer number (2194614).

Almost surely, 2^81671728 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 81671728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (87784560).

81671728 is an abundant number, since it is smaller than the sum of its proper divisors (93897392).

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

81671728 is a wasteful number, since it uses less digits than its factorization.

81671728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 254 (or 248 counting only the distinct ones).

The product of its digits is 37632, while the sum is 40.

The square root of 81671728 is about 9037.2411719507. The cubic root of 81671728 is about 433.8676286543.

The spelling of 81671728 in words is "eighty-one million, six hundred seventy-one thousand, seven hundred twenty-eight".