81081817 has 2 divisors, whose sum is σ = 81081818. Its totient is φ = 81081816.

The previous prime is 81081779. The next prime is 81081827. The reversal of 81081817 is 71818018.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 81072016 + 9801 = 9004^2 + 99^2 .

It is a cyclic number.

It is not a de Polignac number, because 81081817 - 2¹⁵ = 81049049 is a prime.

It is a super-2 number, since 2×81081817² = 13148522096042978, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81081827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40540908 + 40540909.

It is an arithmetic number, because the mean of its divisors is an integer number (40540909).

Almost surely, 2^81081817 is an apocalyptic number.

It is an amenable number.

81081817 is a deficient number, since it is larger than the sum of its proper divisors (1).

81081817 is an equidigital number, since it uses as much as digits as its factorization.

81081817 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 81081817 is about 9004.5442416593. The cubic root of 81081817 is about 432.8205017405.

The spelling of 81081817 in words is "eighty-one million, eighty-one thousand, eight hundred seventeen".