21500320 has 48 divisors (see below), whose sum is σ = 51438240. Its totient is φ = 8491264.

The previous prime is 21500309. The next prime is 21500321. The reversal of 21500320 is 2300512.

It is a plaindrome in base 11.

It is a zygodrome in base 3 and base 11.

It is a self number, because there is not a number n which added to its sum of digits gives 21500320.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21500321) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12471 + ... + 14089.

It is an arithmetic number, because the mean of its divisors is an integer number (1071630).

Almost surely, 2^21500320 is an apocalyptic number.

21500320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21500320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25719120).

21500320 is an abundant number, since it is smaller than the sum of its proper divisors (29937920).

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

21500320 is a wasteful number, since it uses less digits than its factorization.

21500320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1717 (or 1709 counting only the distinct ones).

The product of its (nonzero) digits is 60, while the sum is 13.

The square root of 21500320 is about 4636.8437541069. The cubic root of 21500320 is about 278.0662678660.

Adding to 21500320 its reverse (2300512), we get a palindrome (23800832).

The spelling of 21500320 in words is "twenty-one million, five hundred thousand, three hundred twenty".