21020320 has 48 divisors (see below), whose sum is σ = 50319360. Its totient is φ = 8296704.

The previous prime is 21020303. The next prime is 21020339. The reversal of 21020320 is 2302012.

It is a Harshad number since it is a multiple of its sum of digits (10).

It is a junction number, because it is equal to n+sod(n) for n = 21020297 and 21020306.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11809 + ... + 13471.

It is an arithmetic number, because the mean of its divisors is an integer number (1048320).

Almost surely, 2^21020320 is an apocalyptic number.

21020320 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 21020320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25159680).

21020320 is an abundant number, since it is smaller than the sum of its proper divisors (29299040).

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

21020320 is a wasteful number, since it uses less digits than its factorization.

21020320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1757 (or 1749 counting only the distinct ones).

The product of its (nonzero) digits is 24, while the sum is 10.

The square root of 21020320 is about 4584.7922526544. The cubic root of 21020320 is about 275.9813752047.

Adding to 21020320 its reverse (2302012), we get a palindrome (23322332).

The spelling of 21020320 in words is "twenty-one million, twenty thousand, three hundred twenty".