81955728 has 30 divisors (see below), whose sum is σ = 229362614. Its totient is φ = 27318528.

The previous prime is 81955717. The next prime is 81955747. The reversal of 81955728 is 82755918.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 52012944 + 29942784 = 7212^2 + 5472^2 .

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

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 5 ways as a sum of consecutive naturals, for example, 284425 + ... + 284712.

Almost surely, 2^81955728 is an apocalyptic number.

It is an amenable number.

81955728 is an abundant number, since it is smaller than the sum of its proper divisors (147406886).

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

81955728 is a wasteful number, since it uses less digits than its factorization.

81955728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 569151 (or 569142 counting only the distinct ones).

The product of its digits is 201600, while the sum is 45.

The square root of 81955728 is about 9052.9402958376. The cubic root of 81955728 is about 434.3699479633.

The spelling of 81955728 in words is "eighty-one million, nine hundred fifty-five thousand, seven hundred twenty-eight".