21606004 has 12 divisors (see below), whose sum is σ = 43212064. Its totient is φ = 9259704.

The previous prime is 21605999. The next prime is 21606007. The reversal of 21606004 is 40060612.

21606004 is an admirable number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21606007) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 385794 + ... + 385849.

Almost surely, 2^21606004 is an apocalyptic number.

It is an amenable number.

21606004 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21606004 is a wasteful number, since it uses less digits than its factorization.

21606004 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 771654 (or 771652 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 19.

The square root of 21606004 is about 4648.2258981250. The cubic root of 21606004 is about 278.5211314220.

Adding to 21606004 its reverse (40060612), we get a palindrome (61666616).

The spelling of 21606004 in words is "twenty-one million, six hundred six thousand, four".