21006004 has 12 divisors (see below), whose sum is σ = 36813700. Its totient is φ = 10487808.

The previous prime is 21005987. The next prime is 21006017. The reversal of 21006004 is 40060012.

It can be written as a sum of positive squares in 2 ways, for example, as 9796900 + 11209104 = 3130^2 + 3348^2 .

It is a congruent number.

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, 339 + ... + 6490.

Almost surely, 2^21006004 is an apocalyptic number.

It is an amenable number.

21006004 is a deficient number, since it is larger than the sum of its proper divisors (15807696).

21006004 is a wasteful number, since it uses less digits than its factorization.

21006004 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7602 (or 7600 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 21006004 is about 4583.2307382457. The cubic root of 21006004 is about 275.9187081181.

Adding to 21006004 its reverse (40060012), we get a palindrome (61066016).

The spelling of 21006004 in words is "twenty-one million, six thousand, four".