81075809 has 2 divisors, whose sum is σ = 81075810. Its totient is φ = 81075808.

The previous prime is 81075779. The next prime is 81075833. The reversal of 81075809 is 90857018.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 64754209 + 16321600 = 8047^2 + 4040^2 .

It is a cyclic number.

It is not a de Polignac number, because 81075809 - 2¹² = 81071713 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81075859) 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, 40537904 + 40537905.

It is an arithmetic number, because the mean of its divisors is an integer number (40537905).

Almost surely, 2^81075809 is an apocalyptic number.

It is an amenable number.

81075809 is a deficient number, since it is larger than the sum of its proper divisors (1).

81075809 is an equidigital number, since it uses as much as digits as its factorization.

81075809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 20160, while the sum is 38.

The square root of 81075809 is about 9004.2106261460. The cubic root of 81075809 is about 432.8098110995.

The spelling of 81075809 in words is "eighty-one million, seventy-five thousand, eight hundred nine".