21228689 has 4 divisors (see below), whose sum is σ = 21260724. Its totient is φ = 21196656.

The previous prime is 21228677. The next prime is 21228703. The reversal of 21228689 is 98682212.

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 19360000 + 1868689 = 4400^2 + 1367^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21228689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21228629) 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, 15002 + ... + 16355.

It is an arithmetic number, because the mean of its divisors is an integer number (5315181).

Almost surely, 2^21228689 is an apocalyptic number.

It is an amenable number.

21228689 is a deficient number, since it is larger than the sum of its proper divisors (32035).

21228689 is an equidigital number, since it uses as much as digits as its factorization.

21228689 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32034.

The product of its digits is 27648, while the sum is 38.

The square root of 21228689 is about 4607.4601463279. The cubic root of 21228689 is about 276.8902891954.

The spelling of 21228689 in words is "twenty-one million, two hundred twenty-eight thousand, six hundred eighty-nine".