21711856 has 20 divisors (see below), whose sum is σ = 44541792. Its totient is φ = 10217216.

The previous prime is 21711853. The next prime is 21711857. The reversal of 21711856 is 65811712.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21711853) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 39640 + ... + 40183.

Almost surely, 2^21711856 is an apocalyptic number.

It is an amenable number.

21711856 is an abundant number, since it is smaller than the sum of its proper divisors (22829936).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21711856 is a wasteful number, since it uses less digits than its factorization.

21711856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79848 (or 79842 counting only the distinct ones).

The product of its digits is 3360, while the sum is 31.

The square root of 21711856 is about 4659.5982659453. The cubic root of 21711856 is about 278.9752336456.

It can be divided in two parts, 217 and 11856, that multiplied together give a palindrome (2572752).

The spelling of 21711856 in words is "twenty-one million, seven hundred eleven thousand, eight hundred fifty-six".