81752809 has 2 divisors, whose sum is σ = 81752810. Its totient is φ = 81752808.

The previous prime is 81752807. The next prime is 81752831. The reversal of 81752809 is 90825718.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 51194025 + 30558784 = 7155^2 + 5528^2 .

It is a cyclic number.

It is not a de Polignac number, because 81752809 - 2¹ = 81752807 is a prime.

It is a super-3 number, since 3×81752809³ (a number of 25 digits) contains 333 as substring.

Together with 81752807, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (81752807) 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, 40876404 + 40876405.

It is an arithmetic number, because the mean of its divisors is an integer number (40876405).

Almost surely, 2^81752809 is an apocalyptic number.

It is an amenable number.

81752809 is a deficient number, since it is larger than the sum of its proper divisors (1).

81752809 is an equidigital number, since it uses as much as digits as its factorization.

81752809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 40320, while the sum is 40.

The square root of 81752809 is about 9041.7259967331. The cubic root of 81752809 is about 434.0111576623.

The spelling of 81752809 in words is "eighty-one million, seven hundred fifty-two thousand, eight hundred nine".