81855079 has 2 divisors, whose sum is σ = 81855080. Its totient is φ = 81855078.

The previous prime is 81855077. The next prime is 81855113. The reversal of 81855079 is 97055818.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81855079 - 2¹ = 81855077 is a prime.

Together with 81855077, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81855073) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40927539 + 40927540.

It is an arithmetic number, because the mean of its divisors is an integer number (40927540).

Almost surely, 2^81855079 is an apocalyptic number.

81855079 is a deficient number, since it is larger than the sum of its proper divisors (1).

81855079 is an equidigital number, since it uses as much as digits as its factorization.

81855079 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 100800, while the sum is 43.

The square root of 81855079 is about 9047.3796759062. The cubic root of 81855079 is about 434.1920600104.

The spelling of 81855079 in words is "eighty-one million, eight hundred fifty-five thousand, seventy-nine".