21688324 has 12 divisors (see below), whose sum is σ = 43376704. Its totient is φ = 9294984.

The previous prime is 21688307. The next prime is 21688343. The reversal of 21688324 is 42388612.

21688324 is an admirable number.

It is a self number, because there is not a number n which added to its sum of digits gives 21688324.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 387264 + ... + 387319.

Almost surely, 2^21688324 is an apocalyptic number.

It is an amenable number.

21688324 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21688324 is a wasteful number, since it uses less digits than its factorization.

21688324 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 774594 (or 774592 counting only the distinct ones).

The product of its digits is 18432, while the sum is 34.

The square root of 21688324 is about 4657.0724709843. The cubic root of 21688324 is about 278.8744098015.

The spelling of 21688324 in words is "twenty-one million, six hundred eighty-eight thousand, three hundred twenty-four".