128320861 has 2 divisors, whose sum is σ = 128320862. Its totient is φ = 128320860.

The previous prime is 128320831. The next prime is 128320877. The reversal of 128320861 is 168023821.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 101384761 + 26936100 = 10069^2 + 5190^2 .

It is a cyclic number.

It is not a de Polignac number, because 128320861 - 2²¹ = 126223709 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (128320831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64160430 + 64160431.

It is an arithmetic number, because the mean of its divisors is an integer number (64160431).

Almost surely, 2^128320861 is an apocalyptic number.

It is an amenable number.

128320861 is a deficient number, since it is larger than the sum of its proper divisors (1).

128320861 is an equidigital number, since it uses as much as digits as its factorization.

128320861 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4608, while the sum is 31.

The square root of 128320861 is about 11327.8798104500. The cubic root of 128320861 is about 504.3891722582.

The spelling of 128320861 in words is "one hundred twenty-eight million, three hundred twenty thousand, eight hundred sixty-one".