81656847 has 6 divisors (see below), whose sum is σ = 117948792. Its totient is φ = 54437892.

The previous prime is 81656819. The next prime is 81656873. The reversal of 81656847 is 74865618.

It is a happy number.

81656847 is a `hidden beast` number, since 81 + 6 + 568 + 4 + 7 = 666.

It is a de Polignac number, because none of the positive numbers 2^k-81656847 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81656807) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4536483 + ... + 4536500.

It is an arithmetic number, because the mean of its divisors is an integer number (19658132).

Almost surely, 2^81656847 is an apocalyptic number.

81656847 is a deficient number, since it is larger than the sum of its proper divisors (36291945).

81656847 is a wasteful number, since it uses less digits than its factorization.

81656847 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9072989 (or 9072986 counting only the distinct ones).

The product of its digits is 322560, while the sum is 45.

The square root of 81656847 is about 9036.4178190254. The cubic root of 81656847 is about 433.8412760984.

The spelling of 81656847 in words is "eighty-one million, six hundred fifty-six thousand, eight hundred forty-seven".