21023604 has 48 divisors (see below), whose sum is σ = 62294400. Its totient is φ = 6006528.

The previous prime is 21023599. The next prime is 21023623. The reversal of 21023604 is 40632012.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

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 15 ways as a sum of consecutive naturals, for example, 13149 + ... + 14660.

It is an arithmetic number, because the mean of its divisors is an integer number (1297800).

Almost surely, 2^21023604 is an apocalyptic number.

It is an amenable number.

21023604 is an abundant number, since it is smaller than the sum of its proper divisors (41270796).

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

21023604 is a wasteful number, since it uses less digits than its factorization.

21023604 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27829 (or 27821 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 21023604 is about 4585.1503792133. The cubic root of 21023604 is about 275.9957466263.

Adding to 21023604 its reverse (40632012), we get a palindrome (61655616).

The spelling of 21023604 in words is "twenty-one million, twenty-three thousand, six hundred four".