21013320 has 64 divisors (see below), whose sum is σ = 64592640. Its totient is φ = 5465600.

The previous prime is 21013303. The next prime is 21013357. The reversal of 21013320 is 2331012.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a junction number, because it is equal to n+sod(n) for n = 21013296 and 21013305.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2785 + ... + 7055.

It is an arithmetic number, because the mean of its divisors is an integer number (1009260).

Almost surely, 2^21013320 is an apocalyptic number.

21013320 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 21013320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32296320).

21013320 is an abundant number, since it is smaller than the sum of its proper divisors (43579320).

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

21013320 is a wasteful number, since it uses less digits than its factorization.

21013320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4326 (or 4322 counting only the distinct ones).

The product of its (nonzero) digits is 36, while the sum is 12.

The square root of 21013320 is about 4584.0287957211. The cubic root of 21013320 is about 275.9507368492.

Adding to 21013320 its reverse (2331012), we get a palindrome (23344332).

It can be divided in two parts, 210 and 13320, that added together give a triangular number (13530 = T₁₆₄).

The spelling of 21013320 in words is "twenty-one million, thirteen thousand, three hundred twenty".