81664459 has 4 divisors (see below), whose sum is σ = 82473120. Its totient is φ = 80855800.

The previous prime is 81664441. The next prime is 81664463. The reversal of 81664459 is 95446618.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81664459 - 2¹¹ = 81662411 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81664259) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 404179 + ... + 404380.

It is an arithmetic number, because the mean of its divisors is an integer number (20618280).

Almost surely, 2^81664459 is an apocalyptic number.

81664459 is a deficient number, since it is larger than the sum of its proper divisors (808661).

81664459 is a wasteful number, since it uses less digits than its factorization.

81664459 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 808660.

The product of its digits is 207360, while the sum is 43.

The square root of 81664459 is about 9036.8389938075. The cubic root of 81664459 is about 433.8547564833.

The spelling of 81664459 in words is "eighty-one million, six hundred sixty-four thousand, four hundred fifty-nine".