21215604 has 24 divisors (see below), whose sum is σ = 49896448. Its totient is φ = 7015680.

The previous prime is 21215599. The next prime is 21215611. The reversal of 21215604 is 40651212.

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 in 7 ways as a sum of consecutive naturals, for example, 5437 + ... + 8484.

Almost surely, 2^21215604 is an apocalyptic number.

It is an amenable number.

21215604 is an abundant number, since it is smaller than the sum of its proper divisors (28680844).

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

21215604 is a wasteful number, since it uses less digits than its factorization.

21215604 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14055 (or 14053 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 21215604 is about 4606.0399477208. The cubic root of 21215604 is about 276.8333873601.

Adding to 21215604 its reverse (40651212), we get a palindrome (61866816).

The spelling of 21215604 in words is "twenty-one million, two hundred fifteen thousand, six hundred four".