21005228 has 24 divisors (see below), whose sum is σ = 38580864. Its totient is φ = 9993600.

The previous prime is 21005227. The next prime is 21005269. The reversal of 21005228 is 82250012.

It is not an unprimeable number, because it can be changed into a prime (21005227) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6176 + ... + 8952.

It is an arithmetic number, because the mean of its divisors is an integer number (1607536).

Almost surely, 2^21005228 is an apocalyptic number.

It is an amenable number.

21005228 is a deficient number, since it is larger than the sum of its proper divisors (17575636).

21005228 is a wasteful number, since it uses less digits than its factorization.

21005228 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2873 (or 2871 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 20.

The square root of 21005228 is about 4583.1460810234. The cubic root of 21005228 is about 275.9153104299.

The spelling of 21005228 in words is "twenty-one million, five thousand, two hundred twenty-eight".