81309528 has 64 divisors (see below), whose sum is σ = 233164800. Its totient is φ = 26226720.

The previous prime is 81309511. The next prime is 81309563. The reversal of 81309528 is 82590318.

It is a super-2 number, since 2×81309528² = 13222478687165568, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 81309492 and 81309501.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 625 + ... + 12767.

It is an arithmetic number, because the mean of its divisors is an integer number (3643200).

Almost surely, 2^81309528 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 81309528, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (116582400).

81309528 is an abundant number, since it is smaller than the sum of its proper divisors (151855272).

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

81309528 is a wasteful number, since it uses less digits than its factorization.

81309528 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12189 (or 12179 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 36.

The square root of 81309528 is about 9017.1796034015. The cubic root of 81309528 is about 433.2253021954.

The spelling of 81309528 in words is "eighty-one million, three hundred nine thousand, five hundred twenty-eight".