81664879 has 2 divisors, whose sum is σ = 81664880. Its totient is φ = 81664878.

The previous prime is 81664867. The next prime is 81664901. The reversal of 81664879 is 97846618.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81664879 - 2¹¹ = 81662831 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81664859) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40832439 + 40832440.

It is an arithmetic number, because the mean of its divisors is an integer number (40832440).

Almost surely, 2^81664879 is an apocalyptic number.

81664879 is a deficient number, since it is larger than the sum of its proper divisors (1).

81664879 is an equidigital number, since it uses as much as digits as its factorization.

81664879 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 580608, while the sum is 49.

The square root of 81664879 is about 9036.8622319918. The cubic root of 81664879 is about 433.8555002531.

The spelling of 81664879 in words is "eighty-one million, six hundred sixty-four thousand, eight hundred seventy-nine".