21228305 has 24 divisors (see below), whose sum is σ = 29779776. Its totient is φ = 14230080.

The previous prime is 21228289. The next prime is 21228307. The reversal of 21228305 is 50382212.

It is not a de Polignac number, because 21228305 - 2⁴ = 21228289 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21228307) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 130154 + ... + 130316.

It is an arithmetic number, because the mean of its divisors is an integer number (1240824).

Almost surely, 2^21228305 is an apocalyptic number.

It is an amenable number.

21228305 is a deficient number, since it is larger than the sum of its proper divisors (8551471).

21228305 is an equidigital number, since it uses as much as digits as its factorization.

21228305 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 297 (or 236 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 23.

The square root of 21228305 is about 4607.4184745907. The cubic root of 21228305 is about 276.8886196542. Note that the first 3 decimals are identical.

The spelling of 21228305 in words is "twenty-one million, two hundred twenty-eight thousand, three hundred five".