21606228 has 72 divisors (see below), whose sum is σ = 63231168. Its totient is φ = 6092928.

The previous prime is 21606217. The next prime is 21606259. The reversal of 21606228 is 82260612.

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 23 ways as a sum of consecutive naturals, for example, 20400 + ... + 21432.

Almost surely, 2^21606228 is an apocalyptic number.

21606228 is a gapful number since it is divisible by the number (28) 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 21606228, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31615584).

21606228 is an abundant number, since it is smaller than the sum of its proper divisors (41624940).

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

21606228 is a wasteful number, since it uses less digits than its factorization.

21606228 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1133 (or 1128 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 27.

The square root of 21606228 is about 4648.2499932770. The cubic root of 21606228 is about 278.5220939402.

The spelling of 21606228 in words is "twenty-one million, six hundred six thousand, two hundred twenty-eight".