81947529 has 6 divisors (see below), whose sum is σ = 118368666. Its totient is φ = 54631680.

The previous prime is 81947527. The next prime is 81947543. The reversal of 81947529 is 92574918.

81947529 is a `hidden beast` number, since 81 + 9 + 47 + 529 = 666.

It can be written as a sum of positive squares in only one way, i.e., 81866304 + 81225 = 9048^2 + 285^2 .

It is not a de Polignac number, because 81947529 - 2¹ = 81947527 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81947527) 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 5 ways as a sum of consecutive naturals, for example, 4552632 + ... + 4552649.

It is an arithmetic number, because the mean of its divisors is an integer number (19728111).

Almost surely, 2^81947529 is an apocalyptic number.

It is an amenable number.

81947529 is a deficient number, since it is larger than the sum of its proper divisors (36421137).

81947529 is a wasteful number, since it uses less digits than its factorization.

81947529 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9105287 (or 9105284 counting only the distinct ones).

The product of its digits is 181440, while the sum is 45.

The square root of 81947529 is about 9052.4874482100. The cubic root of 81947529 is about 434.3554624271.

The spelling of 81947529 in words is "eighty-one million, nine hundred forty-seven thousand, five hundred twenty-nine".