2128921 has 4 divisors (see below), whose sum is σ = 2138292. Its totient is φ = 2119552.

The previous prime is 2128891. The next prime is 2128933. The reversal of 2128921 is 1298212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 168921 + 1960000 = 411^2 + 1400^2 .

It is a cyclic number.

It is not a de Polignac number, because 2128921 - 2⁹ = 2128409 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2128991) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4336 + ... + 4801.

It is an arithmetic number, because the mean of its divisors is an integer number (534573).

2^2128921 is an apocalyptic number.

It is an amenable number.

2128921 is a deficient number, since it is larger than the sum of its proper divisors (9371).

2128921 is an equidigital number, since it uses as much as digits as its factorization.

2128921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9370.

The product of its digits is 576, while the sum is 25.

The square root of 2128921 is about 1459.0822457970. The cubic root of 2128921 is about 128.6431054188.

The spelling of 2128921 in words is "two million, one hundred twenty-eight thousand, nine hundred twenty-one".