81528221 has 8 divisors (see below), whose sum is σ = 87646080. Its totient is φ = 75593088.

The previous prime is 81528217. The next prime is 81528229. The reversal of 81528221 is 12282518.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81528221 - 2² = 81528217 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81528229) 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, 44756 + ... + 46541.

It is an arithmetic number, because the mean of its divisors is an integer number (10955760).

Almost surely, 2^81528221 is an apocalyptic number.

It is an amenable number.

81528221 is a deficient number, since it is larger than the sum of its proper divisors (6117859).

81528221 is a wasteful number, since it uses less digits than its factorization.

81528221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91363.

The product of its digits is 2560, while the sum is 29.

The square root of 81528221 is about 9029.2979239806. The cubic root of 81528221 is about 433.6133605544.

The spelling of 81528221 in words is "eighty-one million, five hundred twenty-eight thousand, two hundred twenty-one".