21030784 has 32 divisors (see below), whose sum is σ = 42882840. Its totient is φ = 10268160.

The previous prime is 21030781. The next prime is 21030791. The reversal of 21030784 is 48703012.

It is a tau number, because it is divible by the number of its divisors (32).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21030781) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3594 + ... + 7414.

Almost surely, 2^21030784 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21030784, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21441420).

21030784 is an abundant number, since it is smaller than the sum of its proper divisors (21852056).

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

21030784 is an equidigital number, since it uses as much as digits as its factorization.

21030784 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3878 (or 3866 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 25.

The square root of 21030784 is about 4585.9332746999. The cubic root of 21030784 is about 276.0271624881.

Adding to 21030784 its reverse (48703012), we get a palindrome (69733796).

The spelling of 21030784 in words is "twenty-one million, thirty thousand, seven hundred eighty-four".