21211686 has 16 divisors (see below), whose sum is σ = 47137200. Its totient is φ = 7070544.

The previous prime is 21211643. The next prime is 21211709. The reversal of 21211686 is 68611212.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 196351 + ... + 196458.

It is an arithmetic number, because the mean of its divisors is an integer number (2946075).

Almost surely, 2^21211686 is an apocalyptic number.

21211686 is an abundant number, since it is smaller than the sum of its proper divisors (25925514).

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

21211686 is a wasteful number, since it uses less digits than its factorization.

21211686 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 392820 (or 392814 counting only the distinct ones).

The product of its digits is 1152, while the sum is 27.

The square root of 21211686 is about 4605.6146169648. The cubic root of 21211686 is about 276.8163448728.

Adding to 21211686 its reverse (68611212), we get a palindrome (89822898).

The spelling of 21211686 in words is "twenty-one million, two hundred eleven thousand, six hundred eighty-six".