21000004 has 12 divisors (see below), whose sum is σ = 36836800. Its totient is φ = 10475208.

The previous prime is 20999999. The next prime is 21000037. The reversal of 21000004 is 40000012.

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, 4224 + ... + 7735.

Almost surely, 2^21000004 is an apocalyptic number.

It is an amenable number.

21000004 is a deficient number, since it is larger than the sum of its proper divisors (15836796).

21000004 is a wasteful number, since it uses less digits than its factorization.

21000004 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12402 (or 12400 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 7.

The square root of 21000004 is about 4582.5761313916. The cubic root of 21000004 is about 275.8924351551.

Adding to 21000004 its reverse (40000012), we get a palindrome (61000016).

The spelling of 21000004 in words is "twenty-one million, four", and thus it is an aban number.