81328221 has 48 divisors (see below), whose sum is σ = 138378240. Its totient is φ = 45550080.

The previous prime is 81328217. The next prime is 81328231. The reversal of 81328221 is 12282318.

It is not a de Polignac number, because 81328221 - 2² = 81328217 is a prime.

It is a super-2 number, since 2×81328221² = 13228559062049682, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81328201) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 61000 + ... + 62318.

It is an arithmetic number, because the mean of its divisors is an integer number (2882880).

Almost surely, 2^81328221 is an apocalyptic number.

It is an amenable number.

81328221 is a deficient number, since it is larger than the sum of its proper divisors (57050019).

81328221 is a wasteful number, since it uses less digits than its factorization.

81328221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1386 (or 1383 counting only the distinct ones).

The product of its digits is 1536, while the sum is 27.

The square root of 81328221 is about 9018.2160652759. The cubic root of 81328221 is about 433.2584990431.

The spelling of 81328221 in words is "eighty-one million, three hundred twenty-eight thousand, two hundred twenty-one".