128650721 has 2 divisors, whose sum is σ = 128650722. Its totient is φ = 128650720.

The previous prime is 128650693. The next prime is 128650759. The reversal of 128650721 is 127056821.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 101203600 + 27447121 = 10060^2 + 5239^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-128650721 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (128650021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64325360 + 64325361.

It is an arithmetic number, because the mean of its divisors is an integer number (64325361).

Almost surely, 2^128650721 is an apocalyptic number.

It is an amenable number.

128650721 is a deficient number, since it is larger than the sum of its proper divisors (1).

128650721 is an equidigital number, since it uses as much as digits as its factorization.

128650721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6720, while the sum is 32.

The square root of 128650721 is about 11342.4301188061. The cubic root of 128650721 is about 504.8209946224.

The spelling of 128650721 in words is "one hundred twenty-eight million, six hundred fifty thousand, seven hundred twenty-one".