21228264 has 64 divisors (see below), whose sum is σ = 61545600. Its totient is φ = 6766848.

The previous prime is 21228247. The next prime is 21228289. The reversal of 21228264 is 46282212.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a nude number because it is divisible by every one of its digits.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2832 + ... + 7104.

It is an arithmetic number, because the mean of its divisors is an integer number (961650).

Almost surely, 2^21228264 is an apocalyptic number.

21228264 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21228264, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30772800).

21228264 is an abundant number, since it is smaller than the sum of its proper divisors (40317336).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21228264 is a wasteful number, since it uses less digits than its factorization.

21228264 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4311 (or 4301 counting only the distinct ones).

The product of its digits is 3072, while the sum is 27.

The square root of 21228264 is about 4607.4140252424. The cubic root of 21228264 is about 276.8884413947. Note that the first 3 decimals are identical.

It can be divided in two parts, 2122826 and 4, that added together give a triangular number (2122830 = T₂₀₆₀).

The spelling of 21228264 in words is "twenty-one million, two hundred twenty-eight thousand, two hundred sixty-four".