21000404 has 12 divisors (see below), whose sum is σ = 36789984. Its totient is φ = 10488984.

The previous prime is 21000391. The next prime is 21000407. The reversal of 21000404 is 40400012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000407) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2537 + ... + 6959.

It is an arithmetic number, because the mean of its divisors is an integer number (3065832).

Almost surely, 2^21000404 is an apocalyptic number.

It is an amenable number.

21000404 is a deficient number, since it is larger than the sum of its proper divisors (15789580).

21000404 is a wasteful number, since it uses less digits than its factorization.

21000404 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5614 (or 5612 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 11.

The square root of 21000404 is about 4582.6197747577. The cubic root of 21000404 is about 275.8941868416.

Adding to 21000404 its reverse (40400012), we get a palindrome (61400416).

The spelling of 21000404 in words is "twenty-one million, four hundred four", and thus it is an aban number.