81817081 has 2 divisors, whose sum is σ = 81817082. Its totient is φ = 81817080.

The previous prime is 81817069. The next prime is 81817093. The reversal of 81817081 is 18071818.

It is a balanced prime because it is at equal distance from previous prime (81817069) and next prime (81817093).

It can be written as a sum of positive squares in only one way, i.e., 81721600 + 95481 = 9040^2 + 309^2 .

It is a cyclic number.

It is not a de Polignac number, because 81817081 - 2¹⁷ = 81686009 is a prime.

It is a super-2 number, since 2×81817081² = 13388069486721122, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81817031) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40908540 + 40908541.

It is an arithmetic number, because the mean of its divisors is an integer number (40908541).

Almost surely, 2^81817081 is an apocalyptic number.

It is an amenable number.

81817081 is a deficient number, since it is larger than the sum of its proper divisors (1).

81817081 is an equidigital number, since it uses as much as digits as its factorization.

81817081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3584, while the sum is 34.

The square root of 81817081 is about 9045.2794871137. The cubic root of 81817081 is about 434.1248640845.

Adding to 81817081 its reverse (18071818), we get a palindrome (99888899).

The spelling of 81817081 in words is "eighty-one million, eight hundred seventeen thousand, eighty-one".