21680672 has 72 divisors (see below), whose sum is σ = 48882960. Its totient is φ = 9434880.

The previous prime is 21680669. The next prime is 21680689. The reversal of 21680672 is 27608612.

It is a Smith number, since the sum of its digits (32) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 102647 + ... + 102857.

It is an arithmetic number, because the mean of its divisors is an integer number (678930).

Almost surely, 2^21680672 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 21680672, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24441480).

21680672 is an abundant number, since it is smaller than the sum of its proper divisors (27202288).

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

21680672 is a wasteful number, since it uses less digits than its factorization.

21680672 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 266 (or 245 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 32.

The square root of 21680672 is about 4656.2508523489. The cubic root of 21680672 is about 278.8416087730.

The spelling of 21680672 in words is "twenty-one million, six hundred eighty thousand, six hundred seventy-two".