81806464 has 32 divisors (see below), whose sum is σ = 165423600. Its totient is φ = 40288512.

The previous prime is 81806447. The next prime is 81806467. The reversal of 81806464 is 46460818.

It is a tau number, because it is divible by the number of its divisors (32).

It is not an unprimeable number, because it can be changed into a prime (81806467) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3807 + ... + 13345.

Almost surely, 2^81806464 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81806464, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (82711800).

81806464 is an abundant number, since it is smaller than the sum of its proper divisors (83617136).

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

81806464 is an equidigital number, since it uses as much as digits as its factorization.

81806464 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9620 (or 9608 counting only the distinct ones).

The product of its (nonzero) digits is 36864, while the sum is 37.

The square root of 81806464 is about 9044.6925873686. The cubic root of 81806464 is about 434.1060851898.

The spelling of 81806464 in words is "eighty-one million, eight hundred six thousand, four hundred sixty-four".