21028228 has 12 divisors (see below), whose sum is σ = 39630220. Its totient is φ = 9705312.

The previous prime is 21028213. The next prime is 21028229. The reversal of 21028228 is 82282012.

It can be written as a sum of positive squares in 2 ways, for example, as 4528384 + 16499844 = 2128^2 + 4062^2 .

It is not an unprimeable number, because it can be changed into a prime (21028229) 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, 202143 + ... + 202246.

Almost surely, 2^21028228 is an apocalyptic number.

It is an amenable number.

21028228 is a deficient number, since it is larger than the sum of its proper divisors (18601992).

21028228 is a wasteful number, since it uses less digits than its factorization.

21028228 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 404406 (or 404404 counting only the distinct ones).

The product of its (nonzero) digits is 1024, while the sum is 25.

The square root of 21028228 is about 4585.6545879514. The cubic root of 21028228 is about 276.0159796111.

The spelling of 21028228 in words is "twenty-one million, twenty-eight thousand, two hundred twenty-eight".