21730528 has 48 divisors (see below), whose sum is σ = 45601920. Its totient is φ = 10164096.

The previous prime is 21730519. The next prime is 21730531. The reversal of 21730528 is 82503712.

21730528 is a nontrivial binomial coefficient, being equal to C(6593, 2).

It is a junction number, because it is equal to n+sod(n) for n = 21730496 and 21730505.

It is a congruent number.

It is an unprimeable number.

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, 62451 + ... + 62797.

It is an arithmetic number, because the mean of its divisors is an integer number (950040).

Almost surely, 2^21730528 is an apocalyptic number.

21730528 is the 6592-nd triangular number.

21730528 is the 2198-th centered nonagonal number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21730528, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22800960).

21730528 is an abundant number, since it is smaller than the sum of its proper divisors (23871392).

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

21730528 is a wasteful number, since it uses less digits than its factorization.

21730528 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 479 (or 471 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 28.

The square root of 21730528 is about 4661.6014415649. The cubic root of 21730528 is about 279.0551827916.

The spelling of 21730528 in words is "twenty-one million, seven hundred thirty thousand, five hundred twenty-eight".