21243330 has 128 divisors (see below), whose sum is σ = 61689600. Its totient is φ = 5184000.

The previous prime is 21243307. The next prime is 21243331. The reversal of 21243330 is 3334212.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21243331) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 210280 + ... + 210380.

It is an arithmetic number, because the mean of its divisors is an integer number (481950).

Almost surely, 2^21243330 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21243330, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30844800).

21243330 is an abundant number, since it is smaller than the sum of its proper divisors (40446270).

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

21243330 is a wasteful number, since it uses less digits than its factorization.

21243330 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 177 (or 171 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 18.

The square root of 21243330 is about 4609.0487087901. The cubic root of 21243330 is about 276.9539297890.

Adding to 21243330 its reverse (3334212), we get a palindrome (24577542).

The spelling of 21243330 in words is "twenty-one million, two hundred forty-three thousand, three hundred thirty".