81909899 has 2 divisors, whose sum is σ = 81909900. Its totient is φ = 81909898.

The previous prime is 81909887. The next prime is 81909901. The reversal of 81909899 is 99890918.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81909899 is a prime.

Together with 81909901, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81909899.

It is not a weakly prime, because it can be changed into another prime (81909829) 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, 40954949 + 40954950.

It is an arithmetic number, because the mean of its divisors is an integer number (40954950).

Almost surely, 2^81909899 is an apocalyptic number.

81909899 is a deficient number, since it is larger than the sum of its proper divisors (1).

81909899 is an equidigital number, since it uses as much as digits as its factorization.

81909899 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 419904, while the sum is 53.

The square root of 81909899 is about 9050.4087752985. The cubic root of 81909899 is about 434.2889674447.

The spelling of 81909899 in words is "eighty-one million, nine hundred nine thousand, eight hundred ninety-nine".