81611 has 2 divisors, whose sum is σ = 81612. Its totient is φ = 81610.

The previous prime is 81569. The next prime is 81619. The reversal of 81611 is 11618.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81611 - 2⁶ = 81547 is a prime.

It is a Sophie Germain prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81611.

It is not a weakly prime, because it can be changed into another prime (81619) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40805 + 40806.

It is an arithmetic number, because the mean of its divisors is an integer number (40806).

2⁸¹⁶¹¹ is an apocalyptic number.

81611 is a deficient number, since it is larger than the sum of its proper divisors (1).

81611 is an equidigital number, since it uses as much as digits as its factorization.

81611 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 48, while the sum is 17.

The square root of 81611 is about 285.6763903440. The cubic root of 81611 is about 43.3760066151.

The spelling of 81611 in words is "eighty-one thousand, six hundred eleven".