21003320 has 64 divisors (see below), whose sum is σ = 51408000. Its totient is φ = 7722624.

The previous prime is 21003299. The next prime is 21003329. The reversal of 21003320 is 2330012.

It is a super-2 number, since 2×21003320² = 882278902044800, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21003329) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 87761 + ... + 87999.

It is an arithmetic number, because the mean of its divisors is an integer number (803250).

Almost surely, 2^21003320 is an apocalyptic number.

21003320 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 21003320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25704000).

21003320 is an abundant number, since it is smaller than the sum of its proper divisors (30404680).

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

21003320 is a wasteful number, since it uses less digits than its factorization.

21003320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 289 (or 259 counting only the distinct ones).

The product of its (nonzero) digits is 36, while the sum is 11.

The square root of 21003320 is about 4582.9379223376. The cubic root of 21003320 is about 275.9069559645.

Adding to 21003320 its reverse (2330012), we get a palindrome (23333332).

The spelling of 21003320 in words is "twenty-one million, three thousand, three hundred twenty".