81548665947 has 32 divisors (see below), whose sum is σ = 138114332160. Its totient is φ = 46584888480.

The previous prime is 81548665907. The next prime is 81548665981. The reversal of 81548665947 is 74956684518.

81548665947 is a `hidden beast` number, since 8 + 1 + 5 + 486 + 65 + 94 + 7 = 666.

It is not a de Polignac number, because 81548665947 - 2⁶ = 81548665883 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is not an unprimeable number, because it can be changed into a prime (81548665907) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 564793 + ... + 694325.

It is an arithmetic number, because the mean of its divisors is an integer number (4316072880).

Almost surely, 2^81548665947 is an apocalyptic number.

81548665947 is a deficient number, since it is larger than the sum of its proper divisors (56565666213).

81548665947 is a wasteful number, since it uses less digits than its factorization.

81548665947 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 132880 (or 132874 counting only the distinct ones).

The product of its digits is 58060800, while the sum is 63.

The spelling of 81548665947 in words is "eighty-one billion, five hundred forty-eight million, six hundred sixty-five thousand, nine hundred forty-seven".