21389628 has 48 divisors (see below), whose sum is σ = 55494656. Its totient is φ = 6367680.

The previous prime is 21389593. The next prime is 21389629. The reversal of 21389628 is 82698312.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21389629) 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 15 ways as a sum of consecutive naturals, for example, 2625 + ... + 7047.

Almost surely, 2^21389628 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21389628, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27747328).

21389628 is an abundant number, since it is smaller than the sum of its proper divisors (34105028).

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

21389628 is a wasteful number, since it uses less digits than its factorization.

21389628 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4474 (or 4472 counting only the distinct ones).

The product of its digits is 41472, while the sum is 39.

The square root of 21389628 is about 4624.8922149603. The cubic root of 21389628 is about 277.5882488582.

The spelling of 21389628 in words is "twenty-one million, three hundred eighty-nine thousand, six hundred twenty-eight".