81608999 has 2 divisors, whose sum is σ = 81609000. Its totient is φ = 81608998.

The previous prime is 81608981. The next prime is 81609001. The reversal of 81608999 is 99980618.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81608999 is a prime.

Together with 81609001, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81608299) 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 as a sum of consecutive naturals, namely, 40804499 + 40804500.

It is an arithmetic number, because the mean of its divisors is an integer number (40804500).

Almost surely, 2^81608999 is an apocalyptic number.

81608999 is a deficient number, since it is larger than the sum of its proper divisors (1).

81608999 is an equidigital number, since it uses as much as digits as its factorization.

81608999 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 279936, while the sum is 50.

The square root of 81608999 is about 9033.7699217990. The cubic root of 81608999 is about 433.7565210369.

The spelling of 81608999 in words is "eighty-one million, six hundred eight thousand, nine hundred ninety-nine".