81671618 has 16 divisors (see below), whose sum is σ = 142988544. Its totient is φ = 34257120.

The previous prime is 81671599. The next prime is 81671657. The reversal of 81671618 is 81617618.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 61403 + ... + 62718.

It is an arithmetic number, because the mean of its divisors is an integer number (8936784).

Almost surely, 2^81671618 is an apocalyptic number.

81671618 is a deficient number, since it is larger than the sum of its proper divisors (61316926).

81671618 is a wasteful number, since it uses less digits than its factorization.

81671618 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 124177.

The product of its digits is 16128, while the sum is 38.

The square root of 81671618 is about 9037.2350860205. The cubic root of 81671618 is about 433.8674338686.

The spelling of 81671618 in words is "eighty-one million, six hundred seventy-one thousand, six hundred eighteen".