81790861 has 2 divisors, whose sum is σ = 81790862. Its totient is φ = 81790860.

The previous prime is 81790789. The next prime is 81790867. The reversal of 81790861 is 16809718.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 45562500 + 36228361 = 6750^2 + 6019^2 .

It is a cyclic number.

It is not a de Polignac number, because 81790861 - 2¹⁹ = 81266573 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81790867) 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, 40895430 + 40895431.

It is an arithmetic number, because the mean of its divisors is an integer number (40895431).

Almost surely, 2^81790861 is an apocalyptic number.

It is an amenable number.

81790861 is a deficient number, since it is larger than the sum of its proper divisors (1).

81790861 is an equidigital number, since it uses as much as digits as its factorization.

81790861 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 24192, while the sum is 40.

The square root of 81790861 is about 9043.8299961908. The cubic root of 81790861 is about 434.0784843231.

The spelling of 81790861 in words is "eighty-one million, seven hundred ninety thousand, eight hundred sixty-one".