128605681 has 2 divisors, whose sum is σ = 128605682. Its totient is φ = 128605680.

The previous prime is 128605679. The next prime is 128605693. The reversal of 128605681 is 186506821.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 118461456 + 10144225 = 10884^2 + 3185^2 .

It is a cyclic number.

It is not a de Polignac number, because 128605681 - 2¹ = 128605679 is a prime.

It is a super-2 number, since 2×128605681² = 33078842370947522, which contains 22 as substring.

Together with 128605679, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 128605681.

It is not a weakly prime, because it can be changed into another prime (128605621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64302840 + 64302841.

It is an arithmetic number, because the mean of its divisors is an integer number (64302841).

Almost surely, 2^128605681 is an apocalyptic number.

It is an amenable number.

128605681 is a deficient number, since it is larger than the sum of its proper divisors (1).

128605681 is an equidigital number, since it uses as much as digits as its factorization.

128605681 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 23040, while the sum is 37.

The square root of 128605681 is about 11340.4444798253. Note that the first 4 decimals coincide. The cubic root of 128605681 is about 504.7620759436.

It can be divided in two parts, 128605 and 681, that added together give a triangular number (129286 = T₅₀₈).

The spelling of 128605681 in words is "one hundred twenty-eight million, six hundred five thousand, six hundred eighty-one".