21232728 has 192 divisors, whose sum is σ = 70761600. Its totient is φ = 5667840.

The previous prime is 21232723. The next prime is 21232741. The reversal of 21232728 is 82723212.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21232723) by changing a digit.

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 47 ways as a sum of consecutive naturals, for example, 255775 + ... + 255857.

It is an arithmetic number, because the mean of its divisors is an integer number (368550).

Almost surely, 2^21232728 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 21232728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35380800).

21232728 is an abundant number, since it is smaller than the sum of its proper divisors (49528872).

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

21232728 is a wasteful number, since it uses less digits than its factorization.

21232728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 142 (or 135 counting only the distinct ones).

The product of its digits is 2688, while the sum is 27.

The square root of 21232728 is about 4607.8984363807. The cubic root of 21232728 is about 276.9078485928.

It can be divided in two parts, 2123 and 2728, that added together give a triangular number (4851 = T₉₈).

The spelling of 21232728 in words is "twenty-one million, two hundred thirty-two thousand, seven hundred twenty-eight".