21186856 has 32 divisors (see below), whose sum is σ = 40940640. Its totient is φ = 10274368.

The previous prime is 21186839. The next prime is 21186859. The reversal of 21186856 is 65868112.

It is not an unprimeable number, because it can be changed into a prime (21186859) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 45135 + ... + 45601.

It is an arithmetic number, because the mean of its divisors is an integer number (1279395).

Almost surely, 2^21186856 is an apocalyptic number.

It is an amenable number.

21186856 is a deficient number, since it is larger than the sum of its proper divisors (19753784).

21186856 is a wasteful number, since it uses less digits than its factorization.

21186856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 633 (or 629 counting only the distinct ones).

The product of its digits is 23040, while the sum is 37.

The square root of 21186856 is about 4602.9182047914. The cubic root of 21186856 is about 276.7082907004.

The spelling of 21186856 in words is "twenty-one million, one hundred eighty-six thousand, eight hundred fifty-six".