81528720 has 160 divisors (see below), whose sum is σ = 311146752. Its totient is φ = 17197056.

The previous prime is 81528703. The next prime is 81528761. The reversal of 81528720 is 2782518.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 19974 + ... + 23706.

Almost surely, 2^81528720 is an apocalyptic number.

81528720 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81528720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (155573376).

81528720 is an abundant number, since it is smaller than the sum of its proper divisors (229618032).

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

81528720 is a wasteful number, since it uses less digits than its factorization.

81528720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3769 (or 3763 counting only the distinct ones).

The product of its (nonzero) digits is 8960, while the sum is 33.

The square root of 81528720 is about 9029.3255562085. The cubic root of 81528720 is about 433.6142452077.

The spelling of 81528720 in words is "eighty-one million, five hundred twenty-eight thousand, seven hundred twenty".