21305232 has 120 divisors (see below), whose sum is σ = 67704000. Its totient is φ = 6200064.

The previous prime is 21305231. The next prime is 21305237. The reversal of 21305232 is 23250312.

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

It is not an unprimeable number, because it can be changed into a prime (21305231) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 35269 + ... + 35867.

It is an arithmetic number, because the mean of its divisors is an integer number (564200).

Almost surely, 2^21305232 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 21305232, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33852000).

21305232 is an abundant number, since it is smaller than the sum of its proper divisors (46398768).

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

21305232 is a wasteful number, since it uses less digits than its factorization.

21305232 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 645 (or 636 counting only the distinct ones).

The product of its (nonzero) digits is 360, while the sum is 18.

The square root of 21305232 is about 4615.7590925004. The cubic root of 21305232 is about 277.2226788789. Note that the first 3 decimals are identical.

Adding to 21305232 its reverse (23250312), we get a palindrome (44555544).

The spelling of 21305232 in words is "twenty-one million, three hundred five thousand, two hundred thirty-two".