21217604 has 12 divisors (see below), whose sum is σ = 39085200. Its totient is φ = 10050408.

The previous prime is 21217597. The next prime is 21217621. The reversal of 21217604 is 40671212.

It is a self number, because there is not a number n which added to its sum of digits gives 21217604.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 139514 + ... + 139665.

It is an arithmetic number, because the mean of its divisors is an integer number (3257100).

Almost surely, 2^21217604 is an apocalyptic number.

It is an amenable number.

21217604 is a deficient number, since it is larger than the sum of its proper divisors (17867596).

21217604 is a wasteful number, since it uses less digits than its factorization.

21217604 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 279202 (or 279200 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 23.

The square root of 21217604 is about 4606.2570488413. The cubic root of 21217604 is about 276.8420861363.

Adding to 21217604 its reverse (40671212), we get a palindrome (61888816).

The spelling of 21217604 in words is "twenty-one million, two hundred seventeen thousand, six hundred four".