21102856 has 16 divisors (see below), whose sum is σ = 40159440. Its totient is φ = 10393680.

The previous prime is 21102853. The next prime is 21102869. The reversal of 21102856 is 65820112.

It is a self number, because there is not a number n which added to its sum of digits gives 21102856.

It is not an unprimeable number, because it can be changed into a prime (21102853) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19150 + ... + 20221.

It is an arithmetic number, because the mean of its divisors is an integer number (2509965).

Almost surely, 2^21102856 is an apocalyptic number.

It is an amenable number.

21102856 is a deficient number, since it is larger than the sum of its proper divisors (19056584).

21102856 is a wasteful number, since it uses less digits than its factorization.

21102856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39444 (or 39440 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 25.

The square root of 21102856 is about 4593.7844964691. The cubic root of 21102856 is about 276.3421158377.

Adding to 21102856 its reverse (65820112), we get a palindrome (86922968).

The spelling of 21102856 in words is "twenty-one million, one hundred two thousand, eight hundred fifty-six".