81864810 has 64 divisors (see below), whose sum is σ = 219576960. Its totient is φ = 21703680.

The previous prime is 81864803. The next prime is 81864817. The reversal of 81864810 is 1846818.

81864810 is a `hidden beast` number, since 8 + 1 + 8 + 648 + 1 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (81864803) and next prime (81864817).

It is a super-2 number, since 2×81864810² = 13403694232672200, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81864817) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 51325 + ... + 52895.

It is an arithmetic number, because the mean of its divisors is an integer number (3430890).

Almost surely, 2^81864810 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81864810, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (109788480).

81864810 is an abundant number, since it is smaller than the sum of its proper divisors (137712150).

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

81864810 is a wasteful number, since it uses less digits than its factorization.

81864810 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1780 (or 1774 counting only the distinct ones).

The product of its (nonzero) digits is 12288, while the sum is 36.

The square root of 81864810 is about 9047.9174399416. The cubic root of 81864810 is about 434.2092650333.

It can be divided in two parts, 8186 and 4810, that added together give a square (12996 = 114²).

The spelling of 81864810 in words is "eighty-one million, eight hundred sixty-four thousand, eight hundred ten".