21004856 has 16 divisors (see below), whose sum is σ = 40655040. Its totient is φ = 10163520.

The previous prime is 21004847. The next prime is 21004883. The reversal of 21004856 is 65840012.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 42101 + ... + 42596.

It is an arithmetic number, because the mean of its divisors is an integer number (2540940).

Almost surely, 2^21004856 is an apocalyptic number.

It is an amenable number.

21004856 is a deficient number, since it is larger than the sum of its proper divisors (19650184).

21004856 is a wasteful number, since it uses less digits than its factorization.

21004856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 84734 (or 84730 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 26.

The square root of 21004856 is about 4583.1054973675. The cubic root of 21004856 is about 275.9136816116.

Adding to 21004856 its reverse (65840012), we get a palindrome (86844868).

The spelling of 21004856 in words is "twenty-one million, four thousand, eight hundred fifty-six".