21656228 has 24 divisors (see below), whose sum is σ = 42680064. Its totient is φ = 9525600.

The previous prime is 21656227. The next prime is 21656231. The reversal of 21656228 is 82265612.

It is a super-3 number, since 3×21656228³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a junction number, because it is equal to n+sod(n) for n = 21656194 and 21656203.

It is not an unprimeable number, because it can be changed into a prime (21656227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6575 + ... + 9302.

It is an arithmetic number, because the mean of its divisors is an integer number (1778336).

Almost surely, 2^21656228 is an apocalyptic number.

It is an amenable number.

21656228 is a deficient number, since it is larger than the sum of its proper divisors (21023836).

21656228 is a wasteful number, since it uses less digits than its factorization.

21656228 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15923 (or 15921 counting only the distinct ones).

The product of its digits is 11520, while the sum is 32.

The square root of 21656228 is about 4653.6252534986. The cubic root of 21656228 is about 278.7367754992.

Multiplying 21656228 by its sum of digits (32), we get a palindrome (692999296).

The spelling of 21656228 in words is "twenty-one million, six hundred fifty-six thousand, two hundred twenty-eight".