21253604 has 12 divisors (see below), whose sum is σ = 39381804. Its totient is φ = 10001664.

The previous prime is 21253597. The next prime is 21253613. The reversal of 21253604 is 40635212.

It can be written as a sum of positive squares in 2 ways, for example, as 19009600 + 2244004 = 4360^2 + 1498^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21253604.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 156209 + ... + 156344.

It is an arithmetic number, because the mean of its divisors is an integer number (3281817).

Almost surely, 2^21253604 is an apocalyptic number.

It is an amenable number.

21253604 is a deficient number, since it is larger than the sum of its proper divisors (18128200).

21253604 is a wasteful number, since it uses less digits than its factorization.

21253604 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 312574 (or 312572 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 23.

The square root of 21253604 is about 4610.1631207583. The cubic root of 21253604 is about 276.9985707199.

Adding to 21253604 its reverse (40635212), we get a palindrome (61888816).

The spelling of 21253604 in words is "twenty-one million, two hundred fifty-three thousand, six hundred four".