81128428189 has 2 divisors, whose sum is σ = 81128428190. Its totient is φ = 81128428188.

The previous prime is 81128428141. The next prime is 81128428243. The reversal of 81128428189 is 98182482118.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 78492427225 + 2636000964 = 280165^2 + 51342^2 .

It is a cyclic number.

It is not a de Polignac number, because 81128428189 - 2⁷ = 81128428061 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81128428889) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40564214094 + 40564214095.

It is an arithmetic number, because the mean of its divisors is an integer number (40564214095).

Almost surely, 2^81128428189 is an apocalyptic number.

It is an amenable number.

81128428189 is a deficient number, since it is larger than the sum of its proper divisors (1).

81128428189 is an equidigital number, since it uses as much as digits as its factorization.

81128428189 is an evil number, because the sum of its binary digits is even.

The product of its digits is 589824, while the sum is 52.

The spelling of 81128428189 in words is "eighty-one billion, one hundred twenty-eight million, four hundred twenty-eight thousand, one hundred eighty-nine".