21221304 has 64 divisors (see below), whose sum is σ = 60510240. Its totient is φ = 6144000.

The previous prime is 21221303. The next prime is 21221339. The reversal of 21221304 is 40312212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21221303) 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, 3304 + ... + 7304.

Almost surely, 2^21221304 is an apocalyptic number.

21221304 is a gapful number since it is divisible by the number (24) 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 21221304, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30255120).

21221304 is an abundant number, since it is smaller than the sum of its proper divisors (39288936).

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

21221304 is a wasteful number, since it uses less digits than its factorization.

21221304 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4040 (or 4036 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 15.

The square root of 21221304 is about 4606.6586589414. The cubic root of 21221304 is about 276.8581774315.

Adding to 21221304 its reverse (40312212), we get a palindrome (61533516).

The spelling of 21221304 in words is "twenty-one million, two hundred twenty-one thousand, three hundred four".