21232128 has 80 divisors (see below), whose sum is σ = 59121216. Its totient is φ = 6758400.

The previous prime is 21232121. The next prime is 21232157. The reversal of 21232128 is 82123212.

It is a happy number.

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 zygodrome in base 4.

It is not an unprimeable number, because it can be changed into a prime (21232121) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 35028 + ... + 35628.

Almost surely, 2^21232128 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 21232128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29560608).

21232128 is an abundant number, since it is smaller than the sum of its proper divisors (37889088).

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

21232128 is an equidigital number, since it uses as much as digits as its factorization.

21232128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 645 (or 629 counting only the distinct ones).

The product of its digits is 384, while the sum is 21.

The square root of 21232128 is about 4607.8333303191. The cubic root of 21232128 is about 276.9052402567.

The spelling of 21232128 in words is "twenty-one million, two hundred thirty-two thousand, one hundred twenty-eight".