21382530 has 64 divisors (see below), whose sum is σ = 55883520. Its totient is φ = 5204736.

The previous prime is 21382511. The next prime is 21382531. The reversal of 21382530 is 3528312.

21382530 is a nontrivial binomial coefficient, being equal to C(6540, 2).

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21382530.

It is not an unprimeable number, because it can be changed into a prime (21382531) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 42259 + ... + 42761.

It is an arithmetic number, because the mean of its divisors is an integer number (873180).

Almost surely, 2^21382530 is an apocalyptic number.

21382530 is the 6539-th triangular number and also the 3270-th hexagonal number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21382530, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27941760).

21382530 is an abundant number, since it is smaller than the sum of its proper divisors (34500990).

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

21382530 is a wasteful number, since it uses less digits than its factorization.

21382530 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 635.

The product of its (nonzero) digits is 1440, while the sum is 24.

The square root of 21382530 is about 4624.1247820534. The cubic root of 21382530 is about 277.5575402148.

It can be divided in two parts, 21382 and 530, that added together give a palindrome (21912).

The spelling of 21382530 in words is "twenty-one million, three hundred eighty-two thousand, five hundred thirty".