81755909 has 2 divisors, whose sum is σ = 81755910. Its totient is φ = 81755908.

The previous prime is 81755893. The next prime is 81755939. The reversal of 81755909 is 90955718.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 71656225 + 10099684 = 8465^2 + 3178^2 .

It is a cyclic number.

It is not a de Polignac number, because 81755909 - 2⁴ = 81755893 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 81755909.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81755939) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40877954 + 40877955.

It is an arithmetic number, because the mean of its divisors is an integer number (40877955).

Almost surely, 2^81755909 is an apocalyptic number.

It is an amenable number.

81755909 is a deficient number, since it is larger than the sum of its proper divisors (1).

81755909 is an equidigital number, since it uses as much as digits as its factorization.

81755909 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 113400, while the sum is 44.

The square root of 81755909 is about 9041.8974225546. The cubic root of 81755909 is about 434.0166433763.

The spelling of 81755909 in words is "eighty-one million, seven hundred fifty-five thousand, nine hundred nine".