21228255 has 24 divisors (see below), whose sum is σ = 37582272. Its totient is φ = 11079744.

The previous prime is 21228247. The next prime is 21228289. The reversal of 21228255 is 55282212.

It is not a de Polignac number, because 21228255 - 2³ = 21228247 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2904 + ... + 7133.

It is an arithmetic number, because the mean of its divisors is an integer number (1565928).

Almost surely, 2^21228255 is an apocalyptic number.

21228255 is a deficient number, since it is larger than the sum of its proper divisors (16354017).

21228255 is a wasteful number, since it uses less digits than its factorization.

21228255 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10095 (or 10092 counting only the distinct ones).

The product of its digits is 3200, while the sum is 27.

The square root of 21228255 is about 4607.4130485556. The cubic root of 21228255 is about 276.8884022646. Note that the first 3 decimals are identical.

It can be divided in two parts, 2122825 and 5, that added together give a triangular number (2122830 = T₂₀₆₀).

The spelling of 21228255 in words is "twenty-one million, two hundred twenty-eight thousand, two hundred fifty-five".