21128129 has 4 divisors (see below), whose sum is σ = 23048880. Its totient is φ = 19207380.

The previous prime is 21128119. The next prime is 21128131. The reversal of 21128129 is 92182112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21128129 - 2¹⁶ = 21062593 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21128098 and 21128107.

It is not an unprimeable number, because it can be changed into a prime (21128119) 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, 960359 + ... + 960380.

It is an arithmetic number, because the mean of its divisors is an integer number (5762220).

Almost surely, 2^21128129 is an apocalyptic number.

It is an amenable number.

21128129 is a deficient number, since it is larger than the sum of its proper divisors (1920751).

21128129 is a wasteful number, since it uses less digits than its factorization.

21128129 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1920750.

The product of its digits is 576, while the sum is 26.

The square root of 21128129 is about 4596.5344554349. The cubic root of 21128129 is about 276.4523885596.

The spelling of 21128129 in words is "twenty-one million, one hundred twenty-eight thousand, one hundred twenty-nine".