21212928 has 216 divisors, whose sum is σ = 71425536. Its totient is φ = 6220800.

The previous prime is 21212909. The next prime is 21212941. The reversal of 21212928 is 82921212.

It is a tau number, because it is divible by the number of its divisors (216).

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 and also a Zuckerman number because it is divisible by the product of its digits.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 684273 + ... + 684303.

Almost surely, 2^21212928 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 21212928, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35712768).

21212928 is an abundant number, since it is smaller than the sum of its proper divisors (50212608).

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

21212928 is an equidigital number, since it uses as much as digits as its factorization.

21212928 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73 (or 47 counting only the distinct ones).

The product of its digits is 1152, while the sum is 27.

The square root of 21212928 is about 4605.7494504152. The cubic root of 21212928 is about 276.8217475423.

The spelling of 21212928 in words is "twenty-one million, two hundred twelve thousand, nine hundred twenty-eight".