128670721 has 2 divisors, whose sum is σ = 128670722. Its totient is φ = 128670720.

The previous prime is 128670701. The next prime is 128670781. The reversal of 128670721 is 127076821.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 92910321 + 35760400 = 9639^2 + 5980^2 .

It is an emirp because it is prime and its reverse (127076821) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 128670721 - 2¹⁵ = 128637953 is a prime.

It is not a weakly prime, because it can be changed into another prime (128670701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64335360 + 64335361.

It is an arithmetic number, because the mean of its divisors is an integer number (64335361).

Almost surely, 2^128670721 is an apocalyptic number.

It is an amenable number.

128670721 is a deficient number, since it is larger than the sum of its proper divisors (1).

128670721 is an equidigital number, since it uses as much as digits as its factorization.

128670721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9408, while the sum is 34.

The square root of 128670721 is about 11343.3117298256. The cubic root of 128670721 is about 504.8471530371.

The spelling of 128670721 in words is "one hundred twenty-eight million, six hundred seventy thousand, seven hundred twenty-one".