81851618 has 16 divisors (see below), whose sum is σ = 131098176. Its totient is φ = 38235120.

The previous prime is 81851611. The next prime is 81851629. The reversal of 81851618 is 81615818.

It is not an unprimeable number, because it can be changed into a prime (81851611) 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 7 ways as a sum of consecutive naturals, for example, 18713 + ... + 22668.

It is an arithmetic number, because the mean of its divisors is an integer number (8193636).

Almost surely, 2^81851618 is an apocalyptic number.

81851618 is a deficient number, since it is larger than the sum of its proper divisors (49246558).

81851618 is a wasteful number, since it uses less digits than its factorization.

81851618 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41449.

The product of its digits is 15360, while the sum is 38.

The square root of 81851618 is about 9047.1884030344. The cubic root of 81851618 is about 434.1859404150.

The spelling of 81851618 in words is "eighty-one million, eight hundred fifty-one thousand, six hundred eighteen".