128322721 has 2 divisors, whose sum is σ = 128322722. Its totient is φ = 128322720.

The previous prime is 128322679. The next prime is 128322739. The reversal of 128322721 is 127223821.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 126787600 + 1535121 = 11260^2 + 1239^2 .

It is a cyclic number.

It is not a de Polignac number, because 128322721 - 2⁹ = 128322209 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 128322721.

It is not a weakly prime, because it can be changed into another prime (128322791) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64161360 + 64161361.

It is an arithmetic number, because the mean of its divisors is an integer number (64161361).

Almost surely, 2^128322721 is an apocalyptic number.

It is an amenable number.

128322721 is a deficient number, since it is larger than the sum of its proper divisors (1).

128322721 is an equidigital number, since it uses as much as digits as its factorization.

128322721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2688, while the sum is 28.

The square root of 128322721 is about 11327.9619084812. The cubic root of 128322721 is about 504.3916092725.

The spelling of 128322721 in words is "one hundred twenty-eight million, three hundred twenty-two thousand, seven hundred twenty-one".