82805581 has 2 divisors, whose sum is σ = 82805582. Its totient is φ = 82805580.

The previous prime is 82805563. The next prime is 82805599. The reversal of 82805581 is 18550828.

82805581 = 6434² + 6435².

It is a balanced prime because it is at equal distance from previous prime (82805563) and next prime (82805599).

It can be written as a sum of positive squares in only one way, i.e., 41409225 + 41396356 = 6435^2 + 6434^2 .

It is a cyclic number.

It is not a de Polignac number, because 82805581 - 2¹¹ = 82803533 is a prime.

It is a super-3 number, since 3×82805581³ (a number of 25 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a self number, because there is not a number n which added to its sum of digits gives 82805581.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (82805551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 41402790 + 41402791.

It is an arithmetic number, because the mean of its divisors is an integer number (41402791).

Almost surely, 2^82805581 is an apocalyptic number.

82805581 is the 6435-th centered square number.

It is an amenable number.

82805581 is a deficient number, since it is larger than the sum of its proper divisors (1).

82805581 is an equidigital number, since it uses as much as digits as its factorization.

82805581 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 25600, while the sum is 37.

The square root of 82805581 is about 9099.7571945629. The cubic root of 82805581 is about 435.8662107387.

It can be divided in two parts, 8280 and 5581, that added together give a triangular number (13861 = T₁₆₆).

The spelling of 82805581 in words is "eighty-two million, eight hundred five thousand, five hundred eighty-one".