21221204 has 6 divisors (see below), whose sum is σ = 37137114. Its totient is φ = 10610600.

The previous prime is 21221171. The next prime is 21221237. The reversal of 21221204 is 40212212.

It is an interprime number because it is at equal distance from previous prime (21221171) and next prime (21221237).

It can be written as a sum of positive squares in only one way, i.e., 19536400 + 1684804 = 4420^2 + 1298^2 .

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2652647 + ... + 2652654.

It is an arithmetic number, because the mean of its divisors is an integer number (6189519).

Almost surely, 2^21221204 is an apocalyptic number.

It is an amenable number.

21221204 is a deficient number, since it is larger than the sum of its proper divisors (15915910).

21221204 is a wasteful number, since it uses less digits than its factorization.

21221204 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5305305 (or 5305303 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 14.

The square root of 21221204 is about 4606.6478050747. The cubic root of 21221204 is about 276.8577425562.

Adding to 21221204 its reverse (40212212), we get a palindrome (61433416).

The spelling of 21221204 in words is "twenty-one million, two hundred twenty-one thousand, two hundred four".