21128189 has 2 divisors, whose sum is σ = 21128190. Its totient is φ = 21128188.

The previous prime is 21128183. The next prime is 21128197. The reversal of 21128189 is 98182112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11256025 + 9872164 = 3355^2 + 3142^2 .

It is a cyclic number.

It is not a de Polignac number, because 21128189 - 2²⁰ = 20079613 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21128183) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10564094 + 10564095.

It is an arithmetic number, because the mean of its divisors is an integer number (10564095).

Almost surely, 2^21128189 is an apocalyptic number.

It is an amenable number.

21128189 is a deficient number, since it is larger than the sum of its proper divisors (1).

21128189 is an equidigital number, since it uses as much as digits as its factorization.

21128189 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2304, while the sum is 32.

The square root of 21128189 is about 4596.5409820864. The cubic root of 21128189 is about 276.4526502506.

It can be divided in two parts, 2112 and 8189, that added together give a palindrome (10301).

The spelling of 21128189 in words is "twenty-one million, one hundred twenty-eight thousand, one hundred eighty-nine".