81216899 has 2 divisors, whose sum is σ = 81216900. Its totient is φ = 81216898.

The previous prime is 81216857. The next prime is 81216901. The reversal of 81216899 is 99861218.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81216899 is a prime.

Together with 81216901, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81216199) 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, 40608449 + 40608450.

It is an arithmetic number, because the mean of its divisors is an integer number (40608450).

Almost surely, 2^81216899 is an apocalyptic number.

81216899 is a deficient number, since it is larger than the sum of its proper divisors (1).

81216899 is an equidigital number, since it uses as much as digits as its factorization.

81216899 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 62208, while the sum is 44.

The square root of 81216899 is about 9012.0418884956. The cubic root of 81216899 is about 433.0607274903.

The spelling of 81216899 in words is "eighty-one million, two hundred sixteen thousand, eight hundred ninety-nine".