81320428 has 24 divisors (see below), whose sum is σ = 164166912. Its totient is φ = 34524624.

The previous prime is 81320423. The next prime is 81320429. The reversal of 81320428 is 82402318.

It is a super-2 number, since 2×81320428² = 13226024020206368, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a junction number, because it is equal to n+sod(n) for n = 81320396 and 81320405.

It is not an unprimeable number, because it can be changed into a prime (81320423) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10576 + ... + 16567.

It is an arithmetic number, because the mean of its divisors is an integer number (6840288).

Almost surely, 2^81320428 is an apocalyptic number.

It is an amenable number.

81320428 is an abundant number, since it is smaller than the sum of its proper divisors (82846484).

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

81320428 is a wasteful number, since it uses less digits than its factorization.

81320428 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27261 (or 27259 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 28.

The square root of 81320428 is about 9017.7839849932. The cubic root of 81320428 is about 433.2446600940.

The spelling of 81320428 in words is "eighty-one million, three hundred twenty thousand, four hundred twenty-eight".