2128768921 has 2 divisors, whose sum is σ = 2128768922. Its totient is φ = 2128768920.

The previous prime is 2128768847. The next prime is 2128768969. The reversal of 2128768921 is 1298678212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2119313296 + 9455625 = 46036^2 + 3075^2 .

It is a cyclic number.

It is not a de Polignac number, because 2128768921 - 2⁹ = 2128768409 is a prime.

It is not a weakly prime, because it can be changed into another prime (2128768121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1064384460 + 1064384461.

It is an arithmetic number, because the mean of its divisors is an integer number (1064384461).

Almost surely, 2^2128768921 is an apocalyptic number.

It is an amenable number.

2128768921 is a deficient number, since it is larger than the sum of its proper divisors (1).

2128768921 is an equidigital number, since it uses as much as digits as its factorization.

2128768921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 193536, while the sum is 46.

The square root of 2128768921 is about 46138.5838642670. The cubic root of 2128768921 is about 1286.4004214857.

The spelling of 2128768921 in words is "two billion, one hundred twenty-eight million, seven hundred sixty-eight thousand, nine hundred twenty-one".