21206684 has 24 divisors (see below), whose sum is σ = 39534768. Its totient is φ = 9918720.

The previous prime is 21206683. The next prime is 21206687. The reversal of 21206684 is 48660212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21206683) 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, 11447 + ... + 13169.

It is an arithmetic number, because the mean of its divisors is an integer number (1647282).

Almost surely, 2^21206684 is an apocalyptic number.

It is an amenable number.

21206684 is a deficient number, since it is larger than the sum of its proper divisors (18328084).

21206684 is a wasteful number, since it uses less digits than its factorization.

21206684 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1925 (or 1923 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 29.

The square root of 21206684 is about 4605.0715521043. The cubic root of 21206684 is about 276.7945841601.

Adding to 21206684 its reverse (48660212), we get a palindrome (69866896).

The spelling of 21206684 in words is "twenty-one million, two hundred six thousand, six hundred eighty-four".