81996618 has 48 divisors (see below), whose sum is σ = 183744288. Its totient is φ = 24367200.

The previous prime is 81996617. The next prime is 81996619. The reversal of 81996618 is 81669918.

It is an interprime number because it is at equal distance from previous prime (81996617) and next prime (81996619).

81996618 is a strobogrammatic number because it is the same when read upside-down.

It is not an unprimeable number, because it can be changed into a prime (81996611) 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 23 ways as a sum of consecutive naturals, for example, 37413 + ... + 39543.

It is an arithmetic number, because the mean of its divisors is an integer number (3828006).

Almost surely, 2^81996618 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81996618, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (91872144).

81996618 is an abundant number, since it is smaller than the sum of its proper divisors (101747670).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81996618 is a wasteful number, since it uses less digits than its factorization.

81996618 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2211 (or 2200 counting only the distinct ones).

The product of its digits is 186624, while the sum is 48.

The square root of 81996618 is about 9055.1983965013. The cubic root of 81996618 is about 434.4421757157.

It can be divided in two parts, 81 and 996618, that added together give a palindrome (996699).

The spelling of 81996618 in words is "eighty-one million, nine hundred ninety-six thousand, six hundred eighteen".