21228188 has 12 divisors (see below), whose sum is σ = 37181592. Its totient is φ = 10604880.

The previous prime is 21228167. The next prime is 21228209. The reversal of 21228188 is 88182212.

It is an interprime number because it is at equal distance from previous prime (21228167) and next prime (21228209).

It is a congruent number.

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 3 ways as a sum of consecutive naturals, for example, 7898 + ... + 10238.

It is an arithmetic number, because the mean of its divisors is an integer number (3098466).

Almost surely, 2^21228188 is an apocalyptic number.

It is an amenable number.

21228188 is a deficient number, since it is larger than the sum of its proper divisors (15953404).

21228188 is a wasteful number, since it uses less digits than its factorization.

21228188 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4612 (or 4610 counting only the distinct ones).

The product of its digits is 4096, while the sum is 32.

The square root of 21228188 is about 4607.4057776584. The cubic root of 21228188 is about 276.8881109619. Note that the first 3 decimals are identical.

The spelling of 21228188 in words is "twenty-one million, two hundred twenty-eight thousand, one hundred eighty-eight".