21680604 has 72 divisors (see below), whose sum is σ = 60972912. Its totient is φ = 6439680.

The previous prime is 21680587. The next prime is 21680609. The reversal of 21680604 is 40608612.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21680609) 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 23 ways as a sum of consecutive naturals, for example, 20472 + ... + 21504.

It is an arithmetic number, because the mean of its divisors is an integer number (846846).

Almost surely, 2^21680604 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21680604, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30486456).

21680604 is an abundant number, since it is smaller than the sum of its proper divisors (39292308).

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

21680604 is a wasteful number, since it uses less digits than its factorization.

21680604 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1107 (or 1102 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 27.

The square root of 21680604 is about 4656.2435503311. The cubic root of 21680604 is about 278.8413172499.

It can be divided in two parts, 21 and 680604, that added together give a square (680625 = 825²).

The spelling of 21680604 in words is "twenty-one million, six hundred eighty thousand, six hundred four".