21305204 has 6 divisors (see below), whose sum is σ = 37284114. Its totient is φ = 10652600.

The previous prime is 21305203. The next prime is 21305209. The reversal of 21305204 is 40250312.

It can be written as a sum of positive squares in only one way, i.e., 18576100 + 2729104 = 4310^2 + 1652^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21305203) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2663147 + ... + 2663154.

It is an arithmetic number, because the mean of its divisors is an integer number (6214019).

Almost surely, 2^21305204 is an apocalyptic number.

It is an amenable number.

21305204 is a deficient number, since it is larger than the sum of its proper divisors (15978910).

21305204 is a wasteful number, since it uses less digits than its factorization.

21305204 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5326305 (or 5326303 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 17.

The square root of 21305204 is about 4615.7560594122. The cubic root of 21305204 is about 277.2225574339. Note that the first 3 decimals are identical.

Adding to 21305204 its reverse (40250312), we get a palindrome (61555516).

The spelling of 21305204 in words is "twenty-one million, three hundred five thousand, two hundred four".