21021030 has 72 divisors (see below), whose sum is σ = 57771792. Its totient is φ = 5302368.

The previous prime is 21021001. The next prime is 21021043. The reversal of 21021030 is 3012012.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 32167 + ... + 32813.

It is an arithmetic number, because the mean of its divisors is an integer number (802386).

Almost surely, 2^21021030 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21021030, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28885896).

21021030 is an abundant number, since it is smaller than the sum of its proper divisors (36750762).

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

21021030 is a wasteful number, since it uses less digits than its factorization.

21021030 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 698 (or 676 counting only the distinct ones).

The product of its (nonzero) digits is 12, while the sum is 9.

The square root of 21021030 is about 4584.8696818994. The cubic root of 21021030 is about 275.9844824294.

Adding to 21021030 its reverse (3012012), we get a palindrome (24033042).

The spelling of 21021030 in words is "twenty-one million, twenty-one thousand, thirty".